Subject: Swimming is fun
After prepositions (b.v. about, in, off, at, of, without, by, before):
He left without paying
After certain expressions: (b.v. it's no use, it's no good, can't help, can’t stand)
It's no use arguing
After certain verbs: (b.v. mind, enjoy, like fancy, finish, quit, suggest)
I suggested going to the seaside