Prawn Suit

The Exosuit is an unimplemented vehicle.

Despite its name, it is not a suit, but a mecha.

It can currently be added to the player's inventory using the Debug Console by entering the command ITEM EXOSUIT. However, it cannot be placed or used. It is extremely heavy to the point where the player will be pulled down to the ocean floor with it in their inventory.

According to a Twitter status, the player will be able to dock it into the Cyclops, in a fashion similar to the Seamoth, and will be able to use the Exosuit to explore dark and/or deep places.

A 3D model of the Exosuit can be found on Sketchfab.

Recipe
The Exosuit cannot be crafted at the moment, as it has not been fully implemented yet, but the recipe seems to be the following:

Speculation
An artwork published by the developers suggests that the Exosuit will be needed in order to safely cross the Inactive Lava Zone. Whether this is due to pressure - the Inactive Lava Zone is located at a depth of more than 1000 meters - or due to heat is unknown.

Pre-Alpha
In the Pre-Alpha game, the Exosuit was implemented but buggy. It also had jet boosting capabilities but no mining drill, as seen in the Sketchfab Model shown below.