Start here https://www.instructables.com/id/Underwater-Housing-for-miniDV/
Those instructions give you the basics and sources for the materials. My design differs a bit in that I use simple bolts rather than spring latches. This was because I needed this in a day and couldn't wait for the latches.
Step 1: Build the "lens" Housing
Use 5-minute epoxy to glue it in. Tape off anywhere epoxy should not go including the face of the lens. Lay a bead of epoxy right in front of the flat side of the interior flange. Press the Acrylic into it. Lay another thing bead around the face.
Peel the tape while the epoxy is wet.
Step 2: Cut the Pipe to Length
Clean the pipe.
Step 3: Build the Template for the Acrylic Ring and Back Plate
The back plate and ring have the exact same outer design. The ring simply has the hole cut out of the center for the PVC pipe to fit through. Buld however many bolt holes you like.
Use a drill and jig saw to cut the rough shape out. Use a drum sander to get right to the line. Drill the 1/4" holes in the template. The template is now finiished.
Step 4: Build the Acrylic Back Plate and Ring
Place a 1/4 inch dowel in the hole aligning the two pieces. Drill the next hole and dowel it to align it. Then drill and dowel the final hole.
Use a router with a flush trim bit to trim off the excess. For the photo I removed the paper backing. It is best to leave the backing in place, or replace it with masking tape. This will keep the acrylic from scratching.
Step 5: Assemble the Body
Place the acrylic ring and the pvc ring on the pipe. The PVC ring placement is critical. It must be below the rim of the pipe less than the 1/4 inch o-ring thickness so that the o-ring has room to compress. 3/16" is not a bad distance. Mark and PVC cement the ring in place.
PVC cement the front lens assembly on. Just press it all the way on and turn it a bit to seat it right.
If you forgot to put the acrylic ring on, return to step 1.
Step 6: Build the Inner Plate
Test fit your camera inside the housing. Press it up against the top and sight under it. Build a plate that is wide enough to push the camera against the top a bit. This will help stabilize it.
Glue small strips on either side of the plate inside the housing to keep it from rotating.
Locate and drill a 1/4" hole under the tripod mount hole. Cut a 1/4x20 bolt to length and put a nut on it to hold the plate to the camera.
Slide the assembl into the camera.
Step 7: Mounting
For my purpose, I am mounting the camera to a boat. A hose clamp around a board gives me the clamping surface for my temporary installation.
There have been suggestions about magnetically operating the start/stop button. But for now I operate the camera by starting it up and letting it run. I can edit the footage later. Sound is heavily muffles as you would expect.