diff --git a/CMakeLists.txt b/CMakeLists.txt
index c0bb271..72ff2e7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -183,13 +183,18 @@ if(SEASTACK_ENABLE_CHRONO)
             "  (or /usr/local/opt/libomp on Intel Homebrew).")
     endif()
 
-    # If Chrono set HDF5_DIR, retry the find
+    # If Chrono set HDF5_DIR to NOTFOUND (common when Chrono itself found HDF5
+    # via module mode, not hdf5-config.cmake), clear it so later FindHDF5
+    # module-mode discovery (e.g. Ubuntu libhdf5-dev) can succeed.
     if(NOT HDF5_FOUND AND DEFINED CACHE{HDF5_DIR})
         if("${HDF5_DIR}" MATCHES "NOTFOUND")
             unset(HDF5_DIR CACHE)
             find_package(HDF5 CONFIG QUIET)
         endif()
     endif()
+    if(SEASTACK_ENABLE_HYDRO_IO AND NOT HDF5_FOUND)
+        find_package(HDF5 QUIET COMPONENTS CXX)
+    endif()
 
     # Use same C++ standard as Chrono for ABI compatibility
     if(DEFINED CHRONO_CXX_STANDARD)
diff --git a/apps/seastack/gui/vsg_config.h b/apps/seastack/gui/vsg_config.h
index bfe5bad..99d237d 100644
--- a/apps/seastack/gui/vsg_config.h
+++ b/apps/seastack/gui/vsg_config.h
@@ -25,14 +25,7 @@ inline constexpr int kColorVariationCycle = 8;
 inline constexpr float kWaterR = 0.01f;
 inline constexpr float kWaterG = 0.20f;
 inline constexpr float kWaterB = 0.35f;
-// NOTE: Material opacity must stay at 1.0 on Linux.
-// With opacity < 1.0, Chrono's wrapIfTransparent() wraps the runtime-added
-// water node in vsg::DepthSorted (bin 10), which crashes the VSG renderer
-// at vsg::Bin::add during the first record traversal. The animated water
-// surface is added to the scene after pVis->Initialize(), bypassing the
-// BindAll() compile path that built-in Chrono demos rely on.
-// TODO: enable proper translucency via a runtime compile traversal.
-inline constexpr float kWaterOpacity = 1.0f;
+inline constexpr float kWaterOpacity = 0.55f;
 inline constexpr float kWaterSpecular = 0.6f;
 inline constexpr float kWaterRoughness = 0.05f;
 inline constexpr float kWaterMetallic = 0.0f;
diff --git a/apps/seastack/gui/vsg_water_surface.cpp b/apps/seastack/gui/vsg_water_surface.cpp
index 6c86e50..ecc097a 100644
--- a/apps/seastack/gui/vsg_water_surface.cpp
+++ b/apps/seastack/gui/vsg_water_surface.cpp
@@ -501,7 +501,7 @@ void AnimatedWaterSurface::InitializeWireframe() {
     // Faint blue-gray material.
     auto wire_material = ::chrono_types::make_shared<::chrono::ChVisualMaterial>();
     wire_material->SetDiffuseColor(::chrono::ChColor(0.1f, 0.2f, 0.3f));
-    wire_material->SetOpacity(1.0f);
+    wire_material->SetOpacity(0.35f);
     wire_material->SetRoughness(0.9f);
     wire_material->SetMetallic(0.0f);
 
diff --git a/apps/seastack/single_run.cpp b/apps/seastack/single_run.cpp
index 56d8918..3c3b36b 100644
--- a/apps/seastack/single_run.cpp
+++ b/apps/seastack/single_run.cpp
@@ -123,7 +123,7 @@ namespace {
 class HCParser : public ::chrono::parsers::ChParserMbsYAML {
   public:
     HCParser() : ChParserMbsYAML() {}
-    void SetScriptDir(const std::string& dir) { m_file_handler.SetReferenceDirectory(dir); }
+    void SetScriptDir(const std::string& dir) { m_script_directory = dir; }
 };
 
 static std::shared_ptr<::chrono::ChBody> FindBodyByName(::chrono::ChSystem& system,
diff --git a/scripts/unix/build.sh b/scripts/unix/build.sh
index f0170f8..4cfbf31 100755
--- a/scripts/unix/build.sh
+++ b/scripts/unix/build.sh
@@ -318,14 +318,15 @@ else
   USE_VSG=0
 fi
 
+# HydroIO / HDF5:
+# Do not force HydroIO OFF merely because build-config.json leaves HDF5Dir empty.
+# On Ubuntu/Debian, libhdf5-dev is discovered by CMake FindHDF5 (module mode)
+# without a config-mode HDF5_DIR. Passing -DHDF5_DIR is optional; Chrono's
+# ChronoConfig may even set HDF5_DIR to NOTFOUND when it used module-mode HDF5.
+# Only --no-hydro-io disables HydroIO here. If CMake cannot find HDF5, configure
+# fails with a clear FindHDF5 error instead of a later missing-header failure.
 if [[ -z "${SEASTACK_HDF5_DIR:-}" && "${NO_HYDRO_IO}" -eq 0 ]]; then
-  echo "   [WARN] HDF5 not found; HydroIO will be disabled." >&2
-  if [[ "${USE_CHRONO}" -eq 1 ]]; then
-    echo "          If Chrono was built without HDF5, set HDF5Dir in build-config.json." >&2
-  else
-    echo "          For Chrono-free builds, set HDF5Dir or use --no-hydro-io." >&2
-  fi
-  NO_HYDRO_IO=1
+  echo "   [INFO] HDF5Dir unset; HydroIO left ON for CMake HDF5 discovery (module/config)." >&2
 fi
 
 if [[ "${MOORDYN}" -eq 1 && ! -f "${REPO_ROOT}/extern/MoorDyn/CMakeLists.txt" ]]; then