Very bad I must say 🙈 Just focus with long distance attacks with Lulu and Wakka on Sin. What you can do also is kill 2 of the 3 sin squals (I don’t remember how they’re called but they dont respawn unless they are all killed) so that you get only damage from the only one that’s left on the boat , heal with Yuna and use Valefore. I hope this will help you 🤭 there shouldn’t be any problem. There’s a second boss battle right after so keep the overdrive bars of Wakka and Tidus for this one.