The reason for the lack of guns in Subnautica is that the game started development around the time of Sandy Hook shooting in 2012 and the games director is a proponent of gun control.
Not trying to spark an argument here, just posting the facts so far as I know them.
I've always felt the whole shtick of "weapons don't kill, people do" to be a very weird, nonsensical oxymoron. Weapons are designed for the sole purpose of harm, and mostly of the lethal kind. The whole argument that "people kill" only works if someone used a baseball bat or frying pan etc.
Ah yes, scout spaceships not allowed to be armed, but allowed to have geological equipment: you know, a terawatt mining laser, anti-meteorite cannons, several 20-kiloton seismic probes... A powerful microwave radiostation is also needed for a scout and so what if it can evaporate ships before it?
The safest method was just stasis rifling them and slashing them in the face about a hundred times in the knife until they keeled over and pray the warpers don't notice you. On the more wild side, breed a bunch of crashfish and launch them with the repulsion cannon.
You can use the Grappling Arm and the Drill Arm in the prawn suit to attach yourself to leviathans and drill them to death. It's risky and may take a while, but it's doable
