diff --git a/seabird/netcdf.py b/seabird/netcdf.py
index 80c988b..2ef4169 100644
--- a/seabird/netcdf.py
+++ b/seabird/netcdf.py
@@ -11,7 +11,8 @@
 
 try:
     import netCDF4
-except:
+except ImportError:
+    netCDF4 = None
     module_logger.warning("netCDF4 is not available.")
 
 
@@ -33,6 +34,12 @@ def cnv2nc(data, filename):
     profile = cnv.fCNV("CTD.cnv")
     cnv2nc(profile, "CTD.nc")
     """
+    if netCDF4 is None:
+        raise ImportError(
+            "netCDF4 is required to export CNV data to NetCDF. "
+            "Install it with `pip install 'seabird[CDF]'` or `pip install netCDF4`."
+        )
+
     logging.info("Saving netcdf output file: %s" % filename)
 
     nc = netCDF4.Dataset(filename, "w", format="NETCDF4")
diff --git a/tests/test_netcdf.py b/tests/test_netcdf.py
new file mode 100644
index 0000000..bf777d3
--- /dev/null
+++ b/tests/test_netcdf.py
@@ -0,0 +1,12 @@
+#!/usr/bin/env python
+
+import pytest
+
+from seabird import netcdf
+
+
+def test_cnv2nc_requires_netcdf4(monkeypatch):
+    monkeypatch.setattr(netcdf, "netCDF4", None)
+
+    with pytest.raises(ImportError, match="pip install 'seabird\\[CDF\\]'"):
+        netcdf.cnv2nc(object(), "output.nc")