It’s pretty unfair that the originators of the doggy paddle can’t even practice their move in public pools. Somewhere near every health-official-approved watering hole is a sign banishing animals — never mind that a kid is more likely than your dog to pee in the pool. Well, at least Scooby can dive in one day a year at Ad Astra swimming pool in Lenexa (83rd Street and Maurer). This year, the city combines its annual Dog Swim and Children’s Pet Fair for a full-fledged pet festival called Tails on the Trails. Activities run from 8:30 a.m. to 4 p.m. today and include horseback riding, doggy yoga, exotic animal displays, and discounted rabies shots and microchips, just in case your pooch gets lost in the deep end. A 45-minute doggy swim session is just $5. For more information, call 913-541-0209.