You slip off your pack and leave it on the rock, then descend into the water. The cold isn't as shocking this time. As you paddle around, you look along the bottom of the water for any vents that might be pushing up some heat to help you warm up, but the head lamp only reveals smooth stone.
In the lamplight, the water appears emerald green, and you can see round cuts into the stone as the water's floor, where untouched vortices from the water's current have acted like drills, cutting into the solid rock.
As you admire the stonework, something else catches your eye. You turn in time to see a flash of scaly green skin. It's not moving fast, but neither are you. You try to kick away, but not before it's able to clamp its jaw around your leg, biting down hard.
You let out a scream that's muffled by the water. The headlamp shines into the beast's eyes, blinding it and causing it to let go. You kick away and swim desperately fast, pulling yourself onto a larger landing than the one you were on. You're now cold, tired, and bleeding pretty badly from your leg. You can see your pack, about twenty yards away on the original rock, separated by the water, and you can't see the lizard anymore. The emerald green pool is now tinged slightly red by your blood. The pack has a first aid kit, but it means trying to cross the water again. It wasn't an alligator, if it were you'd probably already be dead, but it certainly isn't friendly either.