Open to all. Byron Lake Park Pool, 76 Bayview Drive, Oakdale, 631-472-7043, Casamento Pool, Muncey Road, West Islip, 631-224-5442 (closed Aug. 27-30), Timberline Pool, 400 Broadway, Brentwood, 631-436-6031 (closed Aug. 26-29), Hidden Pond Pool, 660 Terry Rd., Hauppauge, 631-232-3222 x201. Open June 28-Sept. 1. All pools offer group and private swim lessons for members and non-members. Daily fee: $3.00, $1.50 seniors resident ID card, $6.00 nonresident; $5.00 and $8.00 waterslide at Byron; lift available (call ahead) and memberships available. Call individual pool for hours