The swimming section was difficult, I had to switch from gamepad to keyboard to do it. I think it would be a good idea to heal the characters at certain points as I was going into fights with hardly any HP and couldn't make a single mistake. Also, it ended kind of abruptly with a game over screen, was that meant to happen? It took me by surprise a bit.
The whole turtle invasion was really cool, I especially liked the voice-acted cutscene with them preparing for war. I've not played the other games so it was a bit hard to get into the rest of the story.