When you arrive on the ship, oh shiiii-- vomits on Sin Anyhow, when you get on the ship, after the scene, be sure to look around the more obvious spots. You can find a Remedy in the cabin, for one. There, also, you can kick a suitcase to get a number of Potions - 0 to 20, in fact. Essentially, it works like this: you can get enough Potions to build your stock up to 20, but you will get no more Potions beyond that. For example, I have 15 Potions: I get 5 from the suitcase; I have 99 Potions, I get a sore foot from kicking the suitcase. There’s also an Al Bhed Primer Vol. III in the middle of the power room.
As for stuff that matters? In the cabin of the ship, you’ll O’aka XXIII . For now, he’ll request some money from you, and will keep doing so for a while. If you manage to do so, you will end up lowering his prices closer to the middle of the game (along the Mushroom Rock Road). Here’s how it works:
|Amount Given||Price Change (from Baseline)|
|0-100 Gil||+100% (doubled)|
|101-1000 Gil||+50% (x1.5)|
|1001-10,000 Gil||+20% (x1.2)|
|10,001 or more||-30% (x0.7)|
So, basically, pay him over 10,000 Gil or you will have to pay more money. It’s up to you whether to do it, but you have time if you don’t somehow have 10,001 Gil on-hand like everyone else at this point. That actually about sums it up. Back on the deck, speak with Yuna, then with Wakka, then with Yuna again as you progress through some scenes … to a boss!
BOSS - Sin, Sinscales
Sin himself won’t do much to you in this fight even though all it would take is him to simply dive waaay down into the ocean to kill you all, he’ll move about on occasion to no effect. (That’s one strong harpoon!) However, he does release Sinscales every now and then, which are slightly buffed-up versions of those from Zanarkand. They won’t do excessive damage, maybe 75~100.
In any case, if you want, it wouldn’t be too bad an idea to grind against the 'Scales. I mean, they’re pretty easy to beat, right? With mild healing from Yuna’s Cure on occasion, you could get quite a bit of AP and Gil. (FYI, to get the 10,001 Gil O’aka wants, you need to kill 455 Sinscales (450 if you throw Sin into the mix)) The 'Scales will come on and on endlessly for the most part; however, they only do so when you kill off three of them. If you kill off just two, you can stop their reproduction (?) and therefore make life a little easier on you.
Anyhow, whether you want to or not, you have to fight Sin eventually. To do this, there are three main methods all focusing on ranged attacks: you can attack with Lulu’s magic, with Wakka’s Blitzball (stick to basic Attacks), or have Yuna Summon Valefor and attack from a distance with him. All work pretty well. I recommend Valefor simply because he’s a bit more of a powerhouse, especially with that Overdrive. Shouldn’t be a big problem of a fight even without Valefor, so long as you can heal ably.
That fight progresses into an underwater one that is legitimately difficult.
BOSS - Sinspawn Echuilles, Sinscales
Echuilles comes allied by ever-more of those annoying Sinscales. Granted, they’re normally not annoying - no less than two minutes ago I recommended you grind on them - but when you’re down to two characters that are already weakened, then, yeah, you have a problem. Echuilles mostly sticks to two attacks. Drain Attack is always used twice in a row, dealing around 50 damage to a character and healing Echuilles for the same. It will use Blender every three turns for about 100~125 damage as well.
So, how to go about this? Well, initially, you’ll probably want Tidus Cheering a bit: this can help boost your Defense against Drain Touch and the 'Scales. Blender is considered magical, so it won’t help that, though. You can also have Wakka hit Echuilles with Dark Attack and, in doing so, pretty much immunize yourself from Drain Touch. Once that’s done, focus on healing before you get into an offense centered against Echuilles - once he dies, it’s over, so don’t worry about the endless array of Sinscales.
After the battle and a cutscene, you’ll arrive on Kilika.