he got rolled around a few times while underwater in a part of the beach that has large rocks; when he finally surfaced he was disorientated (probally due to the fact that he was scared for his life) so he was taken to the hospital (most likely for insurance purposes) to make sure he didnt hit his head, neck or have any other problems. He was pronounced OK and I believe already released from the hospital.
The movie is about 'The Mavericks' which is a stretch of beach which has big waves. The waves were predicted to be good today so the film crew rushed out there hopefully to catch the cast riding some nice waves... the waves ended up being more than expected and more than GBUTL could handle.