After pondering this confusing situation, this is what makes the most sense to me now. I think they were both too drunk to be in 5 to 6 foot waves. They were having fun until suddenly they weren't.
I think he probably did try to help her when they both got dragged out into deeper turbulence----but when he got into sudden trouble he had to focus on himself and he lost track of her. He is probably ashamed and embarrassed that she likely drowned under his watch. But I do think that is most likely what happened.
I don't think he was forcing himself on her , I think it was just a dangerous natural disaster.
The video shows him with his arm around her but she has her arm around his waist and she looks happy with that situation. I think they were both willingly enjoying each other's company and made a very bad choice to wade deeper into the water.