While Jim was swimming in the sea

[Bassim]

I am wondering if my sentences are grammatically correct.

While Jim was swimming in the sea, a powerboat hurtled by him and almost killed him. He stopped swimming and shouted and cursed at the driver who was speeding away towards the open sea.

 

[Charlie Bernstein]

The grammar is fine, the language is natural.

But if he'd stopped swimming, he would have sunk. I'd skip that and just say "He shouted and cursed . . . ."