I'd call these underwater Ukrainian artists gimmicky showboats if the paintings weren't so beautiful. Imagine what Van Gough would have cut off if he had to work underwater.
Under the Black Sea, members of the Ukrainian School of Underwater Painting toil away finding their muse in the murky depths. In addition to having to finish a painting before their scuba tanks run out of air -- 40 minutes -- the underwater artists have to coat their canvases with a waterproof adhesive so that the paint will actually stay put put.
My extensive elementary school finger-painting experience leads me to believe that they're using oil-based paints (acrylics would dissipate too quickly). The depth at which the artists work at is also important. The deeper an artist ventures, the more it distorts the colours in the painting. What looks like red at 20 meters could be brown, or even black once it reaches the surface.
If you happen to be in the Ukraine, an exhibition is being held at Swallow's Nest Castle. Just try to contain your instinct to sing Under the Sea while you're there.