Sapphire Falls pool is beautiful and possibly the largest on property?
Cabana Bay has the lazy river. As noted, there are tubes for purchase (not free) but you can also bring your own tubes/floaties & use the air pump there to fill them. There is underwater music at Cabana Bay, I'd heard that Hard Rock has that but was pleasantly surprised to find it at CB also.
Portofino has a fun water slide, and the pool & resort are nicely themed - however, there aren't readily accessible changing rooms at the main pool, you have to walk across to the smaller pool & use the restroom there as a changing area. I was very surprised by that at an upscale hotel.