A very easy one for underwater photographers on a budget.
For years I had a Godox CF-18 flash taking dust on a shelf.
Those flashes are dirt-cheap and I couldn't care to risk one for diving but I could not find any housing for it until I found a 30m waterproof utility case with the exact same dimensions!
Step 1: Shopping
Step 2: Gluing
- Glue the tripod screw on the back of the case.
- If you are using optical fiber for triggering the flash, you can also use a section of a large pen, that's roughly the same diameter as an Intova optical plug.