All the enemies in the sea except kyzokus are in the water family and are therefore weak to lightning. Until you get LIT2, a big group of sahags isn't worth fighting. Oddeyes have low HP but are still pretty difficult because of their gaze attack. The best things to fight here are sharks and kyzokus.
A MINI GAME!
While on the ship, if you hit A & B together (or hold A and hit B) 55 times, you will get this mini game. It is actually better than the real thing because the tiles never get stuck. If you don't know, the point is to get all the numbers into the right order. My best time for solving it is about 52 seconds.
And your reward for solving it? 100G! If you can't solve it and wish to give up just hit B. The WSC & PSX have a much bigger reward for beating it. You get 100G, a Potion, Antidote, and Gold Needle every time, but if you come in first place you get 10000G, 5000 for second, and 2000 for third. You can also keep coming back and beating your time to get tons of money.
Following the recommended path will take you to the ElfLand Area.