diff --git a/src/virtualship/instruments/ship_underwater_st.py b/src/virtualship/instruments/ship_underwater_st.py
index 088a439f..1e66ba50 100644
--- a/src/virtualship/instruments/ship_underwater_st.py
+++ b/src/virtualship/instruments/ship_underwater_st.py
@@ -58,6 +58,10 @@ class Underwater_STInstrument(Instrument):
     def __init__(self, expedition, from_data):
         """Initialize Underwater_STInstrument."""
         variables = {"S": "so", "T": "thetao"}
+        spacetime_buffer_size = {
+            "latlon": 0.25,  # [degrees]
+            "time": 0.0,  # [days]
+        }
 
         super().__init__(
             expedition,
@@ -65,7 +69,7 @@ def __init__(self, expedition, from_data):
             add_bathymetry=False,
             allow_time_extrapolation=True,
             verbose_progress=False,
-            spacetime_buffer_size=None,
+            spacetime_buffer_size=spacetime_buffer_size,
             limit_spec=None,
             from_data=from_data,
         )