BY BARBARA H. BLECHMAN Memorial Day weekend is the signal for area pools to start up their water pumps and make way for the annual wave of summertime swimmers. But this year there's a new wrinkle: Two pools are turning trendy, with new wave machines that let you body-surf like the pros.

On Saturday, Alexandria's Cameron Run Regional Park will premiere its fan-shaped pool where the waves crest up to four feet, and on Monday, Wild World theme park in Prince George's County will unveil its $2 million, 1,120,000-gallon wave pool. For those into sunning rather than swimming, both facilities have carpeted sundecks.

In any case, it's time to dust off the flippers and mask, stretch out last year's swimsuit, stock up on the suntan juice and head out to the nearest public pool, whether new wave or no wave, and refresh yourself with a cool dip.

Maryland and Virginia pools are ready for action this weekend, while D.C.'s pools will open in mid- June. Most have daily, family and seasonal rates, plus various schedules for swim classes, lap or restricted swims (adults only, for example). Entrance fees are relatively inexpensive and most pools stay open until dusk. Just don't forget to bring a towel and swimsuit.