Is that something similar to the bug that meant you could fire a DPL on land in TFTD?
From ufopedia-TFTD bugs:
X-COM Equipment Glitches
Underwater-only weapons (HydroJet Cannon, Torpedo Launcher, and Disruptor Pulse Launcher, plus the Coelecanth/AquaJet & Displacer/PWT SWS weapons) are able to fire on land during XCOM's reaction-fire phase. This should not be allowed. *