diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9282590..a94fed3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -29,14 +29,9 @@ jobs:
           - arch: arm64
             runner: ubuntu-24.04-arm
     steps:
-      # Without git, actions/checkout downloads an archive, and init.sh can't check out the submodules
-      - name: Install git
-        run: apt-get update && apt-get install -y --no-install-recommends ca-certificates git
       - uses: actions/checkout@v5
       - name: Install dependencies
-        run: |
-          git config --global --add safe.directory '*'
-          ./init.sh
+        run: ./init.sh
       - name: Build
         run: ./build.sh
       - name: Test
diff --git a/.gitmodules b/.gitmodules
deleted file mode 100644
index 82f6e36..0000000
--- a/.gitmodules
+++ /dev/null
@@ -1,7 +0,0 @@
-[submodule "external/openocean-messages"]
-	path = external/openocean-messages
-	url = https://github.com/openocean-software/openocean-messages.git
-[submodule "external/moos-ivp"]
-	path = external/moos-ivp
-	url = https://github.com/GobySoft/moos-ivp.git
-	shallow = true
diff --git a/CMakeLists.txt b/CMakeLists.txt
index ed1c740..ca7663b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,10 +16,11 @@ include(GNUInstallDirs)
 set(CMAKE_INSTALL_RPATH "$ORIGIN/../${CMAKE_INSTALL_LIBDIR}")
 
 find_package(Protobuf REQUIRED)
-find_package(openocean_messages 0.1 REQUIRED COMPONENTS cpp)
+find_package(openocean_messages 0.0.1 REQUIRED COMPONENTS cpp)
 
-# MOOS-IvP's helm libraries (IVP_BUILD_HELM_LIBS_ONLY)
-find_package(IVP CONFIG REQUIRED)
+# MOOS-IvP's helm libraries (IVP_BUILD_HELM_LIBS_ONLY); libivp-helm-dev installs them in a
+# prefix of their own, apart from a full MOOS-IvP
+find_package(IVP CONFIG REQUIRED HINTS /usr/lib/${CMAKE_LIBRARY_ARCHITECTURE}/ivp-helm)
 
 find_package(GOBY 3.0 COMPONENTS zeromq OPTIONAL_COMPONENTS moos)
 if(NOT GOBY_FOUND)
diff --git a/README.md b/README.md
index e6c3ea3..3e8d15f 100644
--- a/README.md
+++ b/README.md
@@ -18,19 +18,17 @@ One way to think of this project is as a generator for the equivalent of the MOO
     - ros: ROS middleware node
   - test: Tests, including replays of MOOS-IvP missions (`test/missions`)
 - launch: Example missions
-- external: Submodules
-  - openocean-messages: [openocean-messages](https://github.com/openocean-software/openocean-messages), for the `Navigation` and `ControlSetpoint` messages
-  - moos-ivp: [MOOS-IvP](https://github.com/GobySoft/moos-ivp), for the IvP solver and behaviors
 
 ## Building
 
 *This section was written by Claude.*
 
-`init.sh` checks out the submodules and installs the Ubuntu packages needed to build them and IvPico. These include Goby3, for the Goby app, adding [packages.gobysoft.org](http://packages.gobysoft.org)'s continuous builds if apt doesn't already have it; `init.sh --no-goby` leaves Goby3 out, and `build.sh` then skips the Goby app. `build.sh` then builds, all in `build/`, and installs each into `build/usr`:
+`init.sh` installs the Ubuntu packages needed to build IvPico:
 
-- openocean-messages, into `build/external/openocean-messages`;
-- MOOS-IvP's helm libraries (`IVP_BUILD_HELM_LIBS_ONLY`, as shared libraries, without MOOS or its apps), into `build/external/moos-ivp`, installed first so that IvPico can `find_package(IVP)`;
-- IvPico, against both.
+- [openocean-messages](https://github.com/openocean-software/openocean-messages), for the `Navigation` and `ControlSetpoint` messages, and MOOS-IvP's helm libraries built without MOOS ([GobySoft's `ivp-without-moos`](https://github.com/GobySoft/moos-ivp/tree/ivp-without-moos)), for the IvP solver and behaviors. Both come from [Open Ocean Software](https://github.com/openocean-software/openocean-build)'s continuous builds (apt.oceansoft.org), added if apt doesn't already have them.
+- Goby3, for the Goby app, adding [packages.gobysoft.org](http://packages.gobysoft.org)'s continuous builds if apt doesn't already have it. `init.sh --no-goby` leaves Goby3 out, and `build.sh` then skips the Goby app.
+
+`build.sh` then builds IvPico in `build/` and installs it into `build/usr`.
 
 ```
 ./init.sh
@@ -40,8 +38,6 @@ ctest --test-dir build
 
 `build.sh` passes any arguments on to IvPico's CMake, and `BUILD_DIR` overrides the build directory. Add `build/usr/bin` to your `PATH` to run the installed apps.
 
-To update a submodule, check out the commit you want in it and commit the new pointer, e.g. `git -C external/openocean-messages pull origin main && git add external/openocean-messages`.
-
 ## Goby app
 
 *This section was written by Claude.*
diff --git a/build.sh b/build.sh
index 3076bf5..ef41fd2 100755
--- a/build.sh
+++ b/build.sh
@@ -1,37 +1,11 @@
 #!/usr/bin/env bash
-# Builds the dependencies from their submodules (openocean-messages, and MOOS-IvP's helm libraries),
-# then IvPico against them, all in BUILD_DIR (default build), and installs them all into
-# BUILD_DIR/usr (e.g. add build/usr/bin to PATH). Arguments are passed on to IvPico's cmake.
+# Builds IvPico in BUILD_DIR (default build) and installs it into BUILD_DIR/usr (e.g. add
+# build/usr/bin to PATH). Arguments are passed on to IvPico's cmake.
 set -euo pipefail
 
 cd "$(dirname "$0")"
-for submodule in openocean-messages moos-ivp; do
-    if [ -z "$(ls -A "external/${submodule}")" ]; then
-        echo "external/${submodule} is empty: run ./init.sh first" >&2
-        exit 1
-    fi
-done
 BUILD_DIR=$(realpath -m "${BUILD_DIR:-build}")
-OPENOCEAN_BUILD_DIR=${BUILD_DIR}/external/openocean-messages
-IVP_BUILD_DIR=${BUILD_DIR}/external/moos-ivp
-PREFIX=${BUILD_DIR}/usr
 
-BUILD_DIR=${OPENOCEAN_BUILD_DIR} external/openocean-messages/build.sh -DBUILD_TESTING=OFF
-cmake --install "${OPENOCEAN_BUILD_DIR}" --prefix "${PREFIX}" > /dev/null
-
-cmake -S external/moos-ivp/ivp/src -B "${IVP_BUILD_DIR}" -G Ninja \
-    -DIVP_BUILD_HELM_LIBS_ONLY=ON -DBUILD_SHARED_LIBS=ON \
-    -DIVP_LIB_DIRECTORY="${IVP_BUILD_DIR}/lib" \
-    -DIVP_INC_DIRECTORY="${IVP_BUILD_DIR}/include" \
-    -DIVP_BIN_DIRECTORY="${IVP_BUILD_DIR}/bin"
-ninja -C "${IVP_BUILD_DIR}"
-# find_package(IVP) only works from an installation
-cmake --install "${IVP_BUILD_DIR}" --prefix "${PREFIX}" > /dev/null
-
-cmake -S . -B "${BUILD_DIR}" -G Ninja \
-    -Dopenocean_messages_DIR="${OPENOCEAN_BUILD_DIR}" \
-    -DIVP_DIR="${PREFIX}/lib/cmake/IVP" \
-    -DCMAKE_INSTALL_PREFIX="${PREFIX}" \
-    "$@"
+cmake -S . -B "${BUILD_DIR}" -G Ninja -DCMAKE_INSTALL_PREFIX="${BUILD_DIR}/usr" "$@"
 ninja -C "${BUILD_DIR}"
 cmake --install "${BUILD_DIR}" > /dev/null
diff --git a/external/moos-ivp b/external/moos-ivp
deleted file mode 160000
index 06f25ec..0000000
--- a/external/moos-ivp
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 06f25ec0da52ec44d421cbe24f3522dd47bef11f
diff --git a/external/openocean-messages b/external/openocean-messages
deleted file mode 160000
index 11a1328..0000000
--- a/external/openocean-messages
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 11a132839af11befb3d858f4a4b3570d9dc013e5
diff --git a/init.sh b/init.sh
index 7eec28b..d426ef8 100755
--- a/init.sh
+++ b/init.sh
@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# Checks out the submodules and installs the Ubuntu packages needed to build them and IvPico.
+# Installs the Ubuntu packages needed to build IvPico.
 #
 # Usage: init.sh [--no-goby]
 #   --no-goby  don't install Goby3 (build.sh then skips the Goby app)
@@ -24,8 +24,6 @@ for arg in "$@"; do
     esac
 done
 
-git submodule update --init --recommend-shallow
-
 SUDO=""
 if [ "$(id -u)" -ne 0 ]; then
     SUDO=sudo
@@ -35,12 +33,33 @@ apt_install() {
     $SUDO env DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends "$@"
 }
 
-# moos-ivp's helm libraries (IVP_BUILD_HELM_LIBS_ONLY) need only CMake and a compiler
 # xz-utils: the replay tests' recorded missions are compressed
 packages=(cmake ninja-build g++ git ca-certificates protobuf-compiler libprotobuf-dev xz-utils)
 $SUDO apt-get update
 apt_install "${packages[@]}"
 
+. /etc/os-release
+
+# openocean-messages and MOOS-IvP's helm libraries (built without MOOS), from Open Ocean
+# Software's continuous builds (apt.oceansoft.org) if apt doesn't have them yet
+oo_policy=$(apt-cache policy libivp-helm-dev)
+if ! grep -q "Candidate: [^(]" <<< "${oo_policy}"; then
+    apt_install curl gpg
+    keyring=/usr/share/keyrings/openocean-continuous.asc
+    fingerprint=DAF08DD7788E6C84C6F8E8D3E59E1A81FECDB228
+    key=$(curl -fsSL https://raw.githubusercontent.com/openocean-software/openocean-build/main/keys/continuous.asc)
+    if ! gpg --show-keys --with-colons <<< "${key}" | grep -q "^fpr:*${fingerprint}:"; then
+        echo "The Open Ocean Software continuous key's fingerprint isn't ${fingerprint}" >&2
+        exit 1
+    fi
+    $SUDO tee "${keyring}" <<< "${key}" > /dev/null
+    printf "Types: deb\nURIs: https://apt.oceansoft.org/continuous/%s-%s\nSuites: %s\nComponents: main\nSigned-By: %s\n" \
+        "${ID}" "${VERSION_CODENAME}" "${VERSION_CODENAME}" "${keyring}" |
+        $SUDO tee /etc/apt/sources.list.d/openocean.sources > /dev/null
+    $SUDO apt-get update
+fi
+apt_install libopenocean-messages-dev libivp-helm-dev
+
 if ${goby}; then
     # Goby3, for src/bin/goby. If apt doesn't have it yet, add packages.gobysoft.org's
     # continuous builds, which have 'goby test' (newer than 3.6.1)
@@ -52,7 +71,6 @@ if ${goby}; then
             curl -fsSL "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x19478082E2F8D3FE" |
                 gpg --dearmor | $SUDO tee "${keyring}" > /dev/null
         fi
-        . /etc/os-release
         echo "deb [signed-by=${keyring}] http://packages.gobysoft.org/${ID}/continuous/ ${VERSION_CODENAME}/" |
             $SUDO tee /etc/apt/sources.list.d/gobysoft_continuous.list > /dev/null
         $SUDO apt-get update
@@ -64,5 +82,3 @@ if ${goby}; then
     # MOOS-IvP's apps need libmoos-ivp but don't depend on it
     apt_install libgoby3-moos-dev goby3-moos moosdb10 moos-ivp-apps moos-ivp-gui libmoos-ivp
 fi
-
-external/openocean-messages/init.sh --cxx
diff --git a/launch/goby/alpha/.gitignore b/launch/goby/alpha/.gitignore
new file mode 100644
index 0000000..47241b6
--- /dev/null
+++ b/launch/goby/alpha/.gitignore
@@ -0,0 +1 @@
+images/
diff --git a/launch/goby/alpha/README.md b/launch/goby/alpha/README.md
index f19539a..0bc01b3 100644
--- a/launch/goby/alpha/README.md
+++ b/launch/goby/alpha/README.md
@@ -38,9 +38,10 @@ As in MOOS-IvP's alpha, the helm parks when the survey is done (pHelmIvP's `park
 
 ## Viewing in pMarineViewer
 
-`viewer.launch` shows the vehicle in pMarineViewer as in MOOS-IvP's alpha mission, with its buttons (DEPLOY, RETURN, ...) working. Start it after `alpha.launch`:
+`viewer.launch` shows the vehicle in pMarineViewer as in MOOS-IvP's alpha mission, with its buttons (DEPLOY, RETURN, ...) working. Start it after `alpha.launch`, having fetched MOOS-IvP's background images once with `get_images.sh`:
 
 ```
+./get_images.sh
 goby_launch viewer.launch
 ```
 
diff --git a/launch/goby/alpha/get_images.sh b/launch/goby/alpha/get_images.sh
new file mode 100755
index 0000000..4793b74
--- /dev/null
+++ b/launch/goby/alpha/get_images.sh
@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+# Downloads the MOOS-IvP background images that set_datum_warp.sh can choose between (those with
+# lat/lon bounds) into images/, for pMarineViewer (viewer.launch).
+set -euo pipefail
+
+cd "$(dirname "$0")"
+mkdir -p images
+url=https://raw.githubusercontent.com/GobySoft/moos-ivp/ivp-without-moos/ivp/data
+for image in forrest19 MIT_SP; do
+    for ext in tif info; do
+        [ -s "images/${image}.${ext}" ] || curl -fsSL -o "images/${image}.${ext}" "${url}/${image}.${ext}"
+    done
+done
+ls images
diff --git a/launch/goby/alpha/set_datum_warp.sh b/launch/goby/alpha/set_datum_warp.sh
index 36ca7c3..28faad8 100755
--- a/launch/goby/alpha/set_datum_warp.sh
+++ b/launch/goby/alpha/set_datum_warp.sh
@@ -38,7 +38,7 @@ while [ $# -gt 0 ]; do
 done
 
 goby_cfgs=(config/*.pb.cfg)
-image_dir=${IVP_IMAGE_DIRS:-../../../external/moos-ivp/ivp/data}
+image_dir=${IVP_IMAGE_DIRS:-images}
 
 # the smallest image whose .info bounds contain the datum
 image_for() {
diff --git a/launch/goby/alpha/viewer.launch b/launch/goby/alpha/viewer.launch
index 8a67761..6c69f65 100755
--- a/launch/goby/alpha/viewer.launch
+++ b/launch/goby/alpha/viewer.launch
@@ -3,5 +3,5 @@
 # pMarineViewer, as in MOOS-IvP's alpha mission (see README.md): start after alpha.launch
 MOOSDB alpha.moos
 pNodeReporter alpha.moos
-[env=IVP_IMAGE_DIRS=${IVP_IMAGE_DIRS:-$PWD/../../../external/moos-ivp/ivp/data}] pMarineViewer alpha.moos
+[env=IVP_IMAGE_DIRS=${IVP_IMAGE_DIRS:-$PWD/images}] pMarineViewer alpha.moos
 [env=GOBY_MOOS_GATEWAY_PLUGINS=${GOBY_MOOS_GATEWAY_PLUGINS:-$PWD/../../../build/usr/lib/libivpico_moos_gateway_plugin.so}] goby_moos_gateway config/moos_gateway.pb.cfg
diff --git a/src/test/missions/README.md b/src/test/missions/README.md
index 0be77bf..eb610fe 100644
--- a/src/test/missions/README.md
+++ b/src/test/missions/README.md
@@ -13,10 +13,10 @@ flowchart LR
 ```
 
 - `missions.txt` lists the missions and the variables poked to start them.
-- `record.sh [mission...]` builds all of MOOS-IvP from `external/moos-ivp` into `build/missions`, runs each mission under pHelmIvP with time warp, and keeps each vehicle's helm inputs and outputs in `fixtures/<mission>`. The "Record missions" workflow runs it on GitHub and uploads the fixtures as an artifact.
+- `record.sh [mission...]` builds all of MOOS-IvP from GobySoft's `ivp-without-moos` branch (the source of the `libivp-helm-dev` package) into `build/missions`, runs each mission under pHelmIvP with time warp, and keeps each vehicle's helm inputs and outputs in `fixtures/<mission>`. The "Record missions" workflow runs it on GitHub and uploads the fixtures as an artifact.
 - `replay <fixture>` feeds the recorded inputs to the IvPico helm at pHelmIvP's iteration times and compares what each helm posted. `replay.cpp` describes what's compared and the tolerances.
 
-Re-record the fixtures whenever `external/moos-ivp` moves.
+Re-record the fixtures whenever `libivp-helm-dev` moves to a new MOOS-IvP.
 
 ## Closed-loop runs under Goby
 
diff --git a/src/test/missions/record.sh b/src/test/missions/record.sh
index fbce1d9..1d28e18 100755
--- a/src/test/missions/record.sh
+++ b/src/test/missions/record.sh
@@ -1,11 +1,13 @@
 #!/usr/bin/env bash
 # Records MOOS-IvP missions under pHelmIvP for the replay tests: builds all of
-# MOOS-IvP from external/moos-ivp, runs each mission in missions.txt headless,
-# and keeps each vehicle's helm inputs and outputs in fixtures/<mission>.
+# MOOS-IvP from GobySoft's ivp-without-moos branch (libivp-helm-dev's source),
+# runs each mission in missions.txt headless, and keeps each vehicle's helm
+# inputs and outputs in fixtures/<mission>.
 #
 # Usage: record.sh [mission...]   (default: every mission in missions.txt)
 #
 # WORK_DIR (default build/missions) holds the MOOS-IvP build and the runs.
+# MOOS_IVP_BRANCH overrides the branch.
 # MOOS_BUILD_ARGS are passed to build-moos.sh, e.g. --with-proj=off.
 set -euo pipefail
 
@@ -14,14 +16,13 @@ root=$(cd "${here}/../../.." && pwd)
 work=$(realpath -m "${WORK_DIR:-${root}/build/missions}")
 moos_ivp=${work}/moos-ivp
 
-# A copy, so that building leaves the submodule clean
 if [ ! -x "${moos_ivp}/ivp/bin/pHelmIvP" ]; then
     rm -rf "${moos_ivp}"
-    mkdir -p "${moos_ivp}"
-    git -C "${root}/external/moos-ivp" archive HEAD | tar -x -C "${moos_ivp}"
+    git clone --depth 1 --branch "${MOOS_IVP_BRANCH:-ivp-without-moos}" \
+        https://github.com/GobySoft/moos-ivp.git "${moos_ivp}"
     (cd "${moos_ivp}" && ./build-moos.sh --minrobot ${MOOS_BUILD_ARGS:-} && ./build-ivp.sh --nogui)
 fi
-export PATH="${moos_ivp}/ivp/bin:${moos_ivp}/build/MOOS/MOOSCore/bin:${moos_ivp}/build/MOOS/MOOSEssentials/bin:${PATH}"
+export PATH="${moos_ivp}/ivp/bin:${moos_ivp}/bin:${moos_ivp}/build/MOOS/MOOSCore/bin:${moos_ivp}/build/MOOS/MOOSEssentials/bin:${PATH}"
 
 # Keeps the log header, pHelmIvP's posts, and every post to a variable pHelmIvP
 # registered, without the duplicate lines pLogger sometimes writes