As someone who was on the product team for a 6000msw video camera, it's probably not filled with mineral oil. I doubt anyone makes subsea camera bodies/optics completely from scratch, and off-the-shelf units are not designed for pressure. In ours we used Sony camera internals, the enclosure was atmospheric, filled with dry nitrogen to reduce condensation, and the sapphire lens was designed to resist 12500psi and reduce distortion from the air-->sapphire-->seawater interface.
rtkwe|4 months ago