Cyclops Depth Module MK1
The Hull Reinforcement Module upgrade is an upgrade that increases the dive depth of the Cyclops by 200 meters. It can be added by placing the module inside a Cyclops's upgrade console located in the engine room.
Currently, the Shell Hull Reinforcement Module and Chelonian Hull Reinforcement Module both require a Hull Reinforcement Module in their recipe.
The effects of the Hull Reinforcement Module stacks with the Chelonian Hull Reinforcement Module and the Shell Hull Reinforcement Module.
Recipe
Speculation
A screenshot by the developers seems to imply that adding this upgrade to the Cyclops will increase its crush depth from 200 to 1200 meters and its safe depth from 100 to 450 meters. However, in a Trello entry by the developers, an increase of the crush depth by 100 meters per Hull Reinforcement Module upgrade installed. It may also be just a temporary upgrade that might get removed in later builds.