Not the UFL-3 but I had a UFL-2 that I gave up trying to use with my EM-5 under water. I know some people have had success but for me the RC mode just didn't work for TTL, and the strobe didn't sync at all in manual mode. I spent a lot of frustrating time trying every possible combination of settings even with the help of Olympus tech support and reading every forum post on the web. I concluded that they are buggy. YMMV
For what it's worth, I switched to a pair of Inon S2000 that perform absolutely perfectly on every shot in both S-TTL and manual modes. Using S-TTL only requires the on camera flash to be set to Fill (not fractional powers). I would have thought that you could get the same results with the Z-240.