Remember that not ALL the water is kept at 80°f. It is kept to a temperature that the Marine Animals prefer. I'm not sure what it is, but I'm pretty sure it is not 80°f. Also remember, that it is salt water, some people forget that and coming from someone who lives on a beach, it is hilarious to watch the people who do and come up with a mouth full of saltwater!
Yes you can cover up and other than the dolphin swim, everything is at your leisure. Also remember that they give you wetsuits to use, which will help keep you warm.
Cheers!