I have been working on the issue of shooting steady macro video. And particularly shooting moving subjects from a tripod base. This is what I came up with for my Nauticam GH5 housing but it can be adapted to work with any housing that has a threaded port in the base.
The design is centered around a single point mount that can swivel to allow tracking shots without giving up the stability of a tripod. Furthermore I wanted to make it in such a way that it could be quickly installed and used, and then just as quickly be removed and stored to deal with the versatility of underwater shooting. I began with a Light N Motion bayonet QD mounting plate and Light N Motion QD Loc Line adapter base. These two products can be purchased for about $60 through Backscatter and several other online retailers. I mounted the base plate using a 1/4-20 stainless screw and two thin nylon washers stacked between the plate and the housing. This allowed me to install the plate snugly with no wobble to the housing but it still allows the plate to swivel with a variable amount of tension. This is all that remains "permanently" attached to the housing. The other side of the QD L&M System I threaded onto the 14-20 center bolt on a triple ball arm clamp in place of the tightening knob. The quick disconnect from Light N Motion is threaded and thus acts as both the quick disconnect attachment for the mounting plate on the housing as well as giving the user the ability to vary the pressure on the triple clamp and adjust the ball mounts on the tripods legs For the Legs themselves I used 1/2 inch Loc-Line segments. I prefer the versatility of Loc-Line for tripods as they are infinitely versatile for all types of terrain and can be shaped to grip, support and even suspend the camera for steady shooting in any situation. Loc-Line also allows the entire two foot tall Tripod system to be rolled up small enough to fit into a BCD or drysuit pocket. I used Nauticam Base mount threaded ball adapters and bolted the Locline base segments to them using stainless bolts and flair washers. You can make the legs as long or as short as you like to suit your own shooting needs and styles. I tipped the legs using stainless nut, washer and bolt spikes to better grip on rocky substrate. Though you may just use the Locline taper nozzle fittings or add another ball base mount adapter to allow ridged arm segments to be attached for extra length. I have included links below for the actual parts I used. Let me know if you have any questions on the details of the system.