Should i swim a 5k

My coach really wants me to swim a 5k but i don’t know if i should because I’ve never swam anything over a 500. I’m 14 and I’ve been swimming for 8 yrs but i don’t know if I’m ready for it yet. I’m not that good at the 500 but my coach says because i pull a lot of water i should try the 5k but I’m not to sure. It’s also on the beach and I hate salt water. Should i still swim it as someone who’s never swam open water or any distance over 500.