The Tadpole Depth Module Mk.1 and Mk.2 raise the Tadpole’s crush-depth rating, letting the vehicle survive progressively deeper water. They sit alongside other Tadpole modules: Cavitation Muffler, Echo Location, Engine Efficiency, Photovoltaic Charger and Strike Armor.
Depth modules are the practical key to the late game. Reaching the Abyssal Trench and the Ancient Turbine by vehicle is impossible without them — and the Alien Ruins questline rewards an Engine Efficiency Upgrade that complements them. They fit the Tadpole’s hardpoint system.