Hat Kata in detail
There's a branch of the highly rated Sea Fun Divers on Kata Noi, while well-established Dive Asia and Rumblefish Adventure also operate out of Kata.
Both of Kata's beaches offer decent surfing from April to November; one-hour private classes costs 1200B and board rental is 200/800B per hour/day.
Hiring stand-up paddleboarding (SUP) kits or kayaks costs 300/900B per hour/day.
Be careful of rip currents, heed the red flags and don't go past the breakers in the rainy season unless you're a strong, experienced swimmer.