I wonder if the absence of any footage is not more a product of the segmentation of the market. It seems to me that the c300II and other similar cameras (sony fs7, panasonic varicam) in the 5-20k price range are addressing a non-existing market, especially when it comes to underwater footage.
On one hand, regular hobby users probably can't justify the price of a full package once you factor in housings, external monitors/recorders, ports, lenses, etc. when compared to DSLR type cameras (or ever action cameras) that are perfectly adequate for their use. On the other hand, professionals that actually need (read, can sell) raw 4k footage are selling to blue-chip natural history or hollywood-type productions productions that turn their noses at anything that isn't a 50k+ Red or Arri...