diff --git a/pyorc/api/transect.py b/pyorc/api/transect.py
index 43c5bb0..625b0d8 100644
--- a/pyorc/api/transect.py
+++ b/pyorc/api/transect.py
@@ -186,6 +186,8 @@ def get_q(self, v_corr=0.9, fill_method="zeros"):
         z = ds["zcoords"].values
         # add filled surface velocities with a logarithmic profile curve fit
         depth = self.camera_config.get_depth(z, self.h_a)
+        # make velocities zero where depth is zero
+        ds["v_eff_nofill"][:, depth<=0] = 0.
         if fill_method == "zeros":
             ds["v_eff"] = ds["v_eff_nofill"].fillna(0.)
         elif fill_method == "log_fit":