I think the Great Bay Temple is just a wee bit harder than the Water Temple. They are both pretty challenging and since they are challenging they are fun to go through, which is grand!
The Water Temple is hard because there are so many keys to collect throughout the dungeon, but other than that the Water Temple is rather easy. The Great Bay Temple on the other hand is harder, but that's mainly because there are so many places to go, I use to get lost over there. But I actually didn't find the Great Bay Temple as challenging as many other people had said before I took on the temple.
The boss fight was also a bit of a disappointment actually, I had only heard that Gyorg would be one of the absolute hardest bosses in the Zelda series. But lost only two hearts to him during our first battle (he was still my favorite boss in Majora's Mask though). And well, Morpha was just pathetic...
But I think what makes the Great Bay Temple harder than the Water Temple is that it's such a big dungeon, and that the boss battle was a wee bit more challenging.
Oh me too, me too. I dread the day I retry MM because of that temple and its boss *shivers*Which one do you guys think is harder i just completed GBT For the first time and i thought it was PAINFUL EXTREMELY PAINFUL it gives me chills just thinking about it