Yeah, this was reported as the wheel of doom, there is youtube video about it.  It's a gamebreaking bug.  Some morons actually made levels with these and upped them so people can play on it.  Naturally it breaks their game too.  Since them I've always backed up my saves before going online incase I come across one of these levels by accident.

Always backup your saves guys! 

As for the water room...im stuck therePablo620

1) Trade your secondary weapon for a grenade launcher, it's is the little room before the water room.

2) Jump down and take cover behind the fallen rectangular cover near the center of the room.

3) Pick off the first two machine gunners with your pistol.

4) You will want to conserve your ammo as much as possible, so when the third guy moves behind one of the pillars on the right side, run up behind him and melee kill him. If can be done, I did it many times.

5) Take cover where he was hiding and arm your grenade launcher. Aim where the next wave of enemies are going to come from. Your objective here is to kill at least one with the grenade launcher. When you've killed one go back to your pistol and finish off the other guy.

6) Facing toward the entrance where you came from, more enemies will drop down from the right. Again try to kill at least one with the grenade laucher, use the pistol on the other.

7) The last wave, two shot-gunners will drop down from the entrance, use your last grenade on them. Finish off the other with the pistol.

When I used the grenade launcher I did this on my first try :D