Really, don't ask.

Imagine the scene:

It's a bright sunny day and there is a gaggle of folks enjoying the lake together. Splashes and laughter and playful screams fill the air. Off by herself is one girl. She is in her mid-twenties and calling for her friends to join her. Ok, and she is hot...Jerry Bruckheimer hot.

Cut to an angle that is under water and looking up at the girls treading legs, a la Jaws. In fact, lets cue the classic Jaw's theme. One step further, lets have whatever is viewing the hot girl from below begin to swim toward her.

Now cut back and forth between veiwing her above water, gaily unaware of what lies beneath and viewing her below water, as the predator.

As the cuts get shorter and the music reaches climax everyone knows what to expect. But when they want zig, we zag: Right when hot girl should be bitten, someone behind her explodes out of the water and desperately gasps for air, completely ruining the surprise.

Or! even better, he just sort of surfaces, face down, with a non-committal "bloop", dead.

See, now that is funny =-D