Our family planned on spending 3 nights in Arenal and 3 nights in MA and one in SJO. One of the days when we are MA area is Mon. and that means the park is closed. What other options are there for hiking and swimming in that area? It seems that a beach should be easy find, except that I've read of polluted waters and rip tides.

Isla Damas, canopy tours, Carara, Tarcoles river tours, maybe rafting.

You could go sailing, horseback riding, or do a mangrove tour.

www.tripadvisor.com/members/natureguide

will have all your options

mangrove tour is totally awesome

I wouldn't worry too much about the beach being closed one of the days you are there. If your hotel has a pool there's that, as well as all of the other activites everyone has mentioned. I beleive there's also zip lining around MA too. We were in MA for 3 days and never even made it to the park. However, we stayed at Tulemar and they have their own private beach, so that played a huge part in the reason. We enjoyed the Damas Mangrove tour, relaxing on the beach and the pool, going to the many different restaurants in the area.

I think you'll find a lot to do!