harpoon gun?
grappling hook, I actually wouldn't mind them in the long run, if there was limit to one a team, I believe this is an impossible feature but to actually use a grapple wire and it stay there, or hooked if you will to something and players can climb up it or slide across it, is very realistic, I just think its impossible for the UT engine.
Plus if there going for the massive seal team feeling, or similar, they will need NVG,moving boats, and not to mention all the other water gear. If they somehow created a map or level with all the players in scubagear,h2o tanks, and fins,guns,etc It could be very appealing, not to mention possible for the fact they have made it so servers choose the skins for maps. But as for now I have no clue period on anything for realism for certain areas. But uh, for the underwater shooting, I would leave it as is, or try to adjust the process of coming up from the water, it always seems to be noisy and loud even though your going very,very slow.