I am all about it. A few years ago Luis made one and gave me one. Not the same as Bryan is making now but it worked. I also made a test one about six years ago from PVC.
I like to shore/beech dive. Long distance surface swims, up to a mile, mean I spend a lot of time swimming on my back, my GPS resting on my tummy and my head swiveling for boat traffic. I might stop along the way and bounce down here and there. A DSV would be a godsend.
And for loitering on the surface when drift diving, it is often many minutes before the boat can come and pick up the group. It is nice not to fight the constant free flow.
Luis gave me the poor man's DSV plug. Then he wanted it back, lol
. Then last summer on the Vandie in Key West it got hooked on something and tore off. I realized a few moments later it was missing and went on a frantic search for it. I could not stand the shame of having lost his PMDSV. I found it