As you enter you must pay an admission fee of around $12.00 USD.
Think of Playa Mia as an all inclusive resort beach. They have tried to have something for everyone here. You can rent shade umbrellas, and hammocks, lounge chairs, volleyball & soccer court, and a bungee trampoline.
There is even talk on the island that they are in negotiations with Carnival to have an all inclusive day pass. There is even talk of them building a "Dolphin Discovery" here. If this is not massive enough the list of things going on here is more than I can cover in this page.