Construction Ship is the T1 naval constructor. They are a good builder in terms of build power and speed - even a single one of these assisting the shipyard almost doubles its output. In addition to the Commander’s build list, they are able to produce more advanced T1 defenses, like the Floating Heavy Laser Turret, and give access to the T2 Shipyard. Each one increases your energy storage capacity by 50.
Use them for assisting the lab and quickly expanding, claiming underwater metal spots with underwater metal extractors.