Not strictly underwater gear, but I'm interested in trading my Canon 17-40L (great for split levels and general underwater use) for a Sigma 85 1.4 (Canon mount). Would be willing to throw in a bit of cash if the 85 is in good shape.
The 17-40 is in perfect working condition. A bit of dust has collected internally, but it's not on any of the elements and does not affect image quality in any way shape or form. The lens has always had a filter on it, and there are no scratches to the front/rear elements or the lens body. I can provide photos upon request.
I recently upgraded to a 16-35L, and have little use for my 17-40 other than as a standard zoom on a backup APS-C camera, but I'd rather trade it than sell it outright.
Canon 17-40mm f/4 L
cosmetically flawless, no bumps or scratches
small amount of internal dust, no scratches
a few small nicks in the rubber seal
flawless rear element
UU07 code: manufactured in July, 2007 
