Idk what's wrong with the beach? (a few of them actually), Forth Zachary is great and there's another one with a shore that you have to go very far to get any depth, great for sitting on your butt in the water on a smooth sand and just chilling. Mallary Square sunsets are amazing, and street performers a good entertainment. Plenty of bars with decent live music (jazz, blues, etc). Generally an extremely laid back place with lots of rich drunk gringos. Do not expect to meet many hot females tho', Miami would be better for that. White population dominates KW, btw (which is nice. No racist

).
As someone said already - food is great. If not into the seafood too much, go to the Commodore restaurant and order one of their steaks. Be warned - you will be filled for a few days after that. Rent a scooter, the place is pretty small, you will be able to see most of it that way. Take a jetski few hours tour around the island, much fun.