Speaking of water based levels,.... I just played level 8 - Marshlands and my game froze due to the pathfinding bug. I was about ready to claim the torture rooms, and was enjoying the map before it hung. I'll skip it and continue with the next one. Unfortunately I think the best approach is to take it out and store it until the pathfinding bug is ever fixed.
On the level itself I liked the constant harassment by the tentacles, made playing the map chaotic and difficult to focus on maximizing the dungeon. I wouldn't drop the tentacles so close to the heart though, and perhaps the others not inside the rooms but in the water outside. Funny how you're so generous with the steal-hero specials that don't work on knights and only knights on the map until some tentacles spawn.
EDIT:
I've played a bit of level 9 - Schizo and I don't know how to proceed. The first time I did not notice the boulder traps so I was too late to take the avatar down. The second time I managed to spawn 3 vampires before he arrived and capture him, but that did not win the level. My objective still said 'slow the avatar down' while I already had him in prison, and I could build no new rooms and research no new spells. On my side of the lava there was nothing to do either.
At this point I cheated to see the entire map,... and still found nothing that would help me get any further. The keeper on the right was walled in tight, the keeper on the left still not. Theoretically I could possess one of my lvl 10 vampires (they got that level fighting the avatar) and slowly fly over the lava and then slowly take out those many, many heroes but that would take forever. I don't know if that's what you want, or there's another way to win. If it is, at least give the player some barracks so he can lead a group of vampires. For now I'll skip this one as well.