Can't find the last passkey. Check my entire map, no question marks, it must be in a save room. Where is it?

[SPOILERS...but also an answer]
 
It's in the same room as the scuba mask. Jump over the rack where you got it and it's under the water. Doesn't show up on the map as a "?" because the mask is in the same room. I had trouble with this one too.
 
Hope that helps.
 
--Vinny

Wow I would have never found it. Awesome, Vinny.

thanks Vinny, Now where is the scuba mask room again?