I have a suggestion: skip the room entirely. It's a trainwreck.
First off, there are a ton of safe spots in it. Even if your players are willing to say "Well, the statues are very clearly traps, but maybe our characters don't know that" and eat a swing from the knight to start things off, they can then make that obvious conclusion, back up, and pepper everything with ranged attacks. Alternatively they can simply move around the dragons and the knight entirely without even bothering to deal with them. This is doubly true since the statues don't have any interrupts, so you can even move right through their attack ranges while scurrying past them. On the other hand, if you do have a player run past the knight & dragon statues alone, he's basically dead if you play the whirlpool straight; being slowed and at -5 to hit means it's going to take him a metric eternity to free himself. And thanks to ye olde "Wall of magic that is immune to weapons, magic, or creativity of any kind" preventing the rest of the party from contributing in any way, he'll be KO'ed well before then.
So you've got much of the room that completely fails to be threatening unless you go out of your way to disarm the traps just because they're there to be disarmed, and you've got the other part that's certain death if the group doesn't move into the area in exactly the same time and/or decides to do something other than attacking the statues while the water level is still rising (such as trying skills or looking for controls to stop the water or destroy the walls, or even just attacking the walls themselves.) And say what you will about the Tomb of Horrors-style deathtraps of days past, but at least they had the decency to kill you and be done with it. The whirlpool trap watches you flail helplessly about for 4 or 5 rounds while most of the party stands idly by saying, "Well, sucks to be him, I guess."
And then to compound things, they add in the asinine "This trap doesn't affect Evil creatures" to explain why this room is allowed to exist right in front of the villain's most important section of the keep. Even just using one of the keep's passwords would be a big step up, but apparently even that went way beyond the level of effort that went into designing this encounter.
This room was responsible for without a doubt the worst session of D&D I've ever played. Seriously, skip it or change it dramatically.