So I used Goughs greatbow and arrows to shoot off its tail it took only 2 shots for it to fall off seems alot better than shooting 30 arrows like it says above
Note that the water enables the lightning bombs to have AoE. So ignore your instinct, and stay close to the entrance on dry land. I found that makes it approach you, and use the 3 hit flurry a lot, which leaves a good opening afterward for one or two hits. Much better time than eating its lightning out in the open, and running out of stamina and health while the abomination just flies around you.
Trying to fight this guy with the Moonlight great sword is actually rough, it does barely any damage because of the magic resistance. With pure melee I didnt have too much trouble because of the low health but when you draw out the fight it actually becomes quite difficult. Its definitely one of the most aggressive fights in the game. As a mage your best bet is using soul/crystal soul spears and then it becomes fairly easy as you can kill it in a few casts. This is the first time in the game where the moonlight great sword doesn't perform well
I actually found this guy to be one of the easiest bosses in the game. He was one of the four that I killed first try (The others being Pinwheel, Moonlight Butterfly and Gwyn).
Although it may have been made easier by the fact that I was playing a dex build and had an easy time keeping up with his mobility.
I beat it with iaito +15 and crest shield. Just shield up every attack he throw excet lightning. Your attack window is when he charge, shield up, and then he will stop, then you hit wit r2.
