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. 31-Sept. 3), Timberline Pool, 400 Broadway, Brentwood, 631-436-6031 (closed Aug. 31-Sept. 3), Hidden Pond Pool, 660 Terry Rd., Hauppauge, 631-232-3222 x201. Open June 27-Sept. 7. All pools offer group and private swim lessons for members and non-members. Daily fee: $3 residents, $1.50 seniors resident ID card, $6 nonresident; $5 and $8 waterslide at Byron; discount cards and memberships available. Call individual pool for hoursHours: Call individual pool for hours & rates beginning June 29.