You can leap across the gaps in the floor, but just barely. Be careful for crumbling floors those fishies in the water look hungry. Go down the hallways and along the slippery catwalks.
You'll have to open it enough to give you some leeway since the door closes once you let go of the wheel. Underwater, find the red wheel and spin it to open up a nearby door. The cage will fall into the water and you'll need to kill the big monster using either the crossbow or your 9mm pistol, both of which fire underwater. Climb up to the top floor and talk to the scientist about what swimming around down there, then go jump into the shark cage and grab the crossbow. Unfortunately you're going to need to go into that water too. After emerging from the water you'll see another scientist dying in a creative way.
