When Tom Morey invented the bodyboard in 1971, his design was meant to be used without fins on the bottom of the board. The rail design of the bodyboard is meant to work in unison with swimfins on your feet to help you hold an edge. If you find yourself sliding out, you need to re-position yourself further on the rail and tail of your board and use your inside leg with swimfin trailing to hold your edge. If you still decide you want to have fins on the board, we carry them along with other similar products, but keep in mind they will severely inhibit your ability to do spinning maneuvers and will slow you down a little. On the plus side, if sliding out is a problem you just can't overcome, they will help in that respect.