"Discovery Cove is a full day adventure with waterways open from 9:00 a.m. - 5:00 p.m. daily. Check in begins at 7:30 a.m."
Head to the aviary first thing when it opens (9am), since the birds are much more interactive and more interested in the food cups in the morning before they fill up.
Arrive in the morning by 7:45ish. You'll get your dolphin swim time, then have time to eat breakfast and get suited up before the aviary opens so you'll be ready.
Lockers are free and plentiful.
It is easy to enjoy the whole day there at a nice relaxed pace. Bop between the 3 main areas (lazy river, snorkeling reef, & aviary) at you leisure with lunch and snacks thrown in whenever you feel like it. It's a great relaxation day in between doing other Orlando parks.
Enjoy your day!