This orange blocky vehicle has a clear plastic bubble on top that closes over the pilot's head. There are two small black propellers on the back, and four functional lights on the front.
The Small Submarine allows the Player to dive beneath the surface of the water, without having to worry about air consumption, regardless of the Character selected. Exiting the submersible underwater will start the air counter, but re-entering it will reset it. It has no other special functions.
This appears to be a unique model, not previously existing in any known LEGO product.