We're inclined to believe the Jack La Lannes of the exercise world who argue that swimming is one of the most effective ways to trim the fat. But that doesn't mean we have to do it in the futureworld pools of spa-land, surrounded by trim souls exercising not to lose weight but, it seems, to rub it in that they don't really need to. Nor are we interested in competing with dozens of others for lanes. We prefer doing it in a pool with character, clean water and wide open space, and there's no better place than the YMCA on Locust. Down below street level, the pool has the feel of a magic mosaic cave: gorgeous navy and tan tile surrounds the pool on both floor and wall; a monster echo accents each strained freestyle splash and kick (and scream -- a 3-year-old's squeal in here will burst your eardrums); glass blocks allow sunlight in from above. The result is both stunning and suitable for lopping off the flab.