Freeze!
The shutter speed of the DSLR plays a major role to freeze fast motions. Sometimes things happened so quickly that our human brain failed to perceive its beauty.
For fast motions such as water splashes(outdoor), any shutter speed above 1/1000 should be able to freeze the water. Shutter speed of 1/8000 was used in Aperture Priority mode for the picture above because I wanted to get a good focus of the girl with big aperture.
It is always interesting to photograph water splash because it can create some interesting patterns:)
The choice of shutter speed varies according to the speed of the motion too. For the photo above, I used only 1/400 and yet there isn't much motion blur except for their legs:p
Well, it doesn't mean that you must freeze fast motions all the time. Sometimes some motion blur will increase the impact visually as well.
And of course, don't forget to do jump shots at the beach:)