Something I have been working on for a while now is underwater 3D photometry.
The subject are a pair of WW2 era Valentine Tanks. Used extensively by the allies, these are duplex drive (DD) variants designed for amphibious landings. These examples were lost during Exercise Smash in 1944, a training exercise leading up to D-Day. A further 5 tanks were lost and sadly six of their crew drowned.
The models are derived from around 700 individual frames, all shot on one dive:-
Firstly, the intact example:-
Secondly, the damaged example:-
The tanks are annotated to highlight a few of their features.