Identify the whole system
Underwater cameras, housings, and wet-mount accessories can share a brand while using different fittings. Write down the exact camera or housing model and the lens or adapter model before searching for a match.
Inspect the sealing surfaces
Look closely at threads, bayonets, O-ring grooves, and mating faces. Dirt, dents, corrosion, or a missing seal can matter more than clean-looking glass. An accessory described as untested should not be assumed watertight.
Test before immersion
A dry fit confirms only that parts appear to connect. Consult the equipment manuals for the intended configuration, replace service items as appropriate, and pressure-test a housing before trusting it with a camera in the water.