Over the past 30 plus years of diving, I have designed and built several items for underwater use. Some of these ranged from my first underwater watch to several underwater cameras and a couple of 2 place wet subs. A lot of these items were built while I was aboard ships in the U.S. Navy. During those years, a lot of scrap metals and plastics were available as as the machinery needed to fashion the material into the proper shape needed for whatever I was building.
Well, those years are long gone. The scrap is still out there, but the fancy and very expensive machinery is no longer available for making the complicated low cost items.
A lot of thought and footwork went into these projects. Most parts are commonly available at hardware stores and a few hours work, combined with care and attention, and you can have some attractive as well as functional products at great savings. If replacement parts are ever needed, most any hardware store can supply them.
I am still active as a diver and use these products myself.
For a modest amount, I share the plans with fellow divers and help them
where needed. I'll match any product built from my plans with much
more expensive commercial products.