YOU SAID:

I sometimes go to the marsh where I can watch some birds eat fish

INTO JAPANESE

私は時々沼に行き鳥が魚を食べているのを見ることができます

BACK INTO ENGLISH

I can sometimes go to the swamp and see the birds eating fish

INTO JAPANESE

私は時々湿地に行き、鳥が魚を食べているのを見ることができる

BACK INTO ENGLISH

I can sometimes go to the swamp and see the birds eating fish