The pokey is one of the most useful shots in beach volleyball, but it's also one that can draw the ref's whistle if done incorrectly. And it's frequently done incorrectly.
Three-time beach Olympian Holly McPeak covers the do's and don'ts of the pokey here, explaining the hand-positioning she uses and talking about the gray area between legal and illegal.
If you do it exactly the way Holly does here, you'll be fine. 
If you do it like a dink in indoor volleyball, you will absolutely get busted by the ref. The middle ground is open to interpretation. As Holly notes in the video, if you use more than 2 fingers and those fingers are beginning to open up, you may get yourself in trouble with a strict ref.
