Student or Learner
I' like to ask about the use of "to go to the sea".
I think this normally means "go sailing in the sea for particular purposes like catching fish".
Does it also mean "to go to the beach, enjoy the sunshine and do some swimming"?
You are nearly right.
Sailors and trawlermen would say they were going to sea (without 'the').
If I wanted to go to the beach to sunbathe and swim, I'd say 'Let's go to the seaside'.