Designed for stealthy underwater attacks, the Type-4 form is based on the combined characteristics of various aquatic species from many worlds. While lacking mechanical propulsion systems such as propellers or jets (a concession made to preserve stealth - the sonar profile of a whale's movement and the sonar profile of a jet drive are quite different), its "natural" propulsion is augmented by Covenant technology. Three "planes" of energy shielding create a crest reminiscent of Hunter spines, which helps steer the creature.

The "Moby Dick" carries a central cargo pod. Under normal circumstances this contains a nutritional mixture for the Lekgolo, but it can be pressurized to carry troops, or outfitted with electronics for a sensor suite.

Something I threw together rather hastily in pen, but I'm rather proud of it. If time allows I may do a tidied-up digital version.

Aquatic action is something Halo's always lacked, really. There's the UNSC aircraft carrier from a level background (I forget which), so presumably it's happened, but we've never really seen it. I thought the Lekgolo would make a good Covenant platform for it, as they don't appear to require air (it's mentioned somewhere that they were found on an orbital debris ring, which presumably did not have an atmosphere).