Been many times and no way would I sleep in. You'll be tired enough at the end of the day, go to bed early.
Getting there early = getting to pick your dolphin time, the earlier the better so the rest of the day is not worrying about getting to your time / enjoying the breakfast that is included / pick your loungers and area where you will keep your stuff, since you are going in hot weather you may want a chair with an umbrella or tucked by some trees.
There is plenty to do for us to open and close it. We alternate between snorkeling, then a different activity, snorkeling, then a different activity. Different would be the lazy river (we do several time), the heated pool area, the aviary, meeting some of the animals, the dolphin swim, breakfast, lunch, snacks, drinks, sit in the water lounge with drinks, explore the water & animal area, listen to the music, some folks do the snooba thing .... just walking around it is so beautiful. At the end of the day you can shower and dress right there.
The lazy river is deep and fast, it goes under 2 waterfalls as you enter and leave aviary, it has sunken treasure so take your mask, grab a noodle because there is nothing lazy about it. It's just beautiful.
It's like being swept away to an island beach and we always want every minute of it ........... in addition to it's expensive so I'm not going to short our day.