diff --git a/seawater/__init__.py b/seawater/__init__.py
index 2ba910a..8e7fcb5 100644
--- a/seawater/__init__.py
+++ b/seawater/__init__.py
@@ -1,5 +1,7 @@
 """Seawater: EOS-80 equation of state."""
 
+import warnings
+
 try:
     from ._version import __version__
 except ImportError:
@@ -62,3 +64,8 @@
     "swvel",
     "temp",
 ]
+
+warnings.warn(
+    "The seawater library is deprecated! Please use gsw instead.",
+    stacklevel=2,
+)