Actually, I thought that the slow under-water walking was quite funny. I'm not sure why, but walking in that suit reminds me of....of....a jolly fat man.
The Selkath voices were pretty annoying, but then so are a lot of the non English voices. The wookies perhaps have the best voices.
I thought that Manaan was one of the more interesting worlds as you had to trick/reason your way out of situations with their courts. But it wasn't that difficult. I don't know if it's even possible for you to get it wrong and have them lock you up.
I found the Selkath to be some of the more challenging enemies. I chose it as the first world to visit because it seemed pretty peaceful(a bunch of fish holding on to their neutrality. Then I found the Selkath would slaughter my team with their poison...