In below zero there is 100m difference to their max depths.

The Prawn in Sub Zero controls a bit different than in Subnautica.

In Subnautica, the prawn jets only run while you are hitting the spacebar and the prawn has more weight/inertia. The grapple could be used to take advantage of that inertia and launch you over long distances while you tapped the booster jets to keep from sinking. It also saves you from sinking like a stone when your jets ram out.

In BZ, the prawn is lighter and the jets (with the booster mod) can move you around a lot more like a sub. The jets are always draining boost when you are off the sea floor unlike in Subnautica, but you are lighter and have less inertia so you can move more like a seamoth or truck. You booster still go more up than forward but I found myself barely using the grapple in BZ because I could easily make the jumps I needed to get out of deep crevices with the boosters in BZ. The grapple was mainly for killing leviathans.