For all intents and purposes, the Poly volcano pool (and the non-themed pool) is really open all the time. But they close the slide when the lifeguards leave for that day. I don't know what time that might be in April - it varies.
I am so surprised that even though they don't have a lifeguard present, they allow swimming. I am shocked actually. Most other hotels state the pool is closed.
I did find some hours, on Tikimans site. It said lifeguard on from 10-12. But then I found a picture of the pool sign and that said 7am-12pm, something like that.
So either way, seems late enough that you can go in it. Thats what I was wondering. So thank you.