Start recording on your phone. Put the brightness all the way down so it just looks like it's off to other people. Carry your phone horizontally by your torso and start following them around. You can check the footage later and find that you have a nice clear, crisp shot of their asses. Also try to actually put the phone into her bathing suit so you get a direct shot. You can walk off and not follow them anymore, then come back and pull the phone out. You can then smell the phone and it'll smell like her ass.
Or you can just gun down everyone and turn the water red. You can then slide your penis in between their dead, bleeding asses. You may want to wash them off first though becuase it will be full of sand, shit, and blood.
