In We Need to go Deeper you will play in three environments: In your submarine, in the biome your submarine dives through and in underwater caves.
Interior of your Submarine
See: Submarines
Here you will repair dents, carry torpedos and access the consoles your sub provides. Also, monsters can break in.
Exterior of your Submarine
See: Biomes
The main view for helmsman and gunner. It's what's around your ship: Rocks, monsters, tons of water.
Caves
See: Cave
From time to time, you will encounter underwater caves. Here you can exit your submarine and go exploring by foot. Although filled with monsters, caves reward you with gold, new items and important upgrades for your submarine.