Getting back to the OPs original post about snorkeling with one of these abominations, DONT DO IT. If you're plan is to simply use it to put your eyeballs under the water to see better while scooping, it could work for that. These are meant for people to float around the surface looking at the underwater world, that is the only thing these masks are made for.
When you talk about "snorkeling" it generally is meant to include diving down to the bottom as well. With a traditional snorkel, you simply blow the water out once you reach the surface. If you REALLY need to, you spit the snorkel out and just take a breath. If you get water inside this, there is no spitting it out, there is no clearing. Water inside this could result in drowning.
If you are interested in actually snorkeling while detecting, then yes you need a weight belt. You also generally dont use a scoop. Once you have a target you pinpoint it, get a visual fix on the location, drop down and fan the sand away to reveal the target. You will learn quickly that you can move a LOT of sand with a little fanning. At time when I don't have a weight belt, I have used my foot to fan the sand away with acceptable results.
