Aqua JoggerAquaJogger Adjustable Width Shoes

I'm not understanding the purpose of these. Can someone give an explanation of how they work and what they do?

Do these have to be worn with a belt?

Are these weighted or are they buoyant? Weight great for legs are but I like buoyant ones for abs.

I don't understand how these can be adjusted. From the photo, it looks like you have no ability to make tighter or looser.