I came into contact with this crazy contraption when visiting a friend of mine that had a pool many years ago. I was looking at what appeared to be resistance bands that were attached to a pole at the side of his pool and was confused. Then I got a bit closer and saw that it had a brand name on it that appeared to be a belt. That was exactly what it is. My friend was a little embarrassed when he explained what it was to me.
I had never heard of this product and that is probably because I don't normally watch informercials but apparently it made the rounds back when people still did that and there were quite a few idiots, like my friend, that actually bought this thing.
The way it works is that it hold you in place in the center of your pool with the adjustable ropes on it and that way you don't have to go through the rigors of actually turning and kicking off the walls to actually get some exercise. You never actually go anywhere and it holds you in place.... just like a rope would. It is essentially a rope but you can buy this easy product that is rope for about 20 times what a length of rope would cost. Does it sound awesome so far? Well it gets better!
The way in which you were meant to secure yourself in place with your overpriced rope was to attach a series of suction cups to the side of the pool and if you take a second to think about this situation, it is understandable that many people who have pools aren't actually going to have a surface that the suction cups will actually attach to and stay there. My friend's pool had a sandstone rock surface on the pool sides that was extremely porous so obviously a suction cup is not going to stick to this. The only surface he could that they would stick to was actually on the interior of the pool but now the rope was going to be non-elevated so your kicks would hit the ropes and dislodge them from the side of the pool and thus he would pull them off from the wall and would no longer be held in place.
Other options were to put the suction cups out to the sides but I don't know if you know anything about suction cups, but they tend to move to the direct point of the source of the force being exerted on them which in this instance would be directly behind you. So even if you did put them out to the sides to allow your legs to kick freely behind you, they would move inward (because of this little thing we have on Earth called physics) until they returned to the center and resulted in you kicking them again anyway.
Later versions of this system had an elevated harness which was essentially a stick that you drove into the ground that costs about 20 times as much as a stick that you could drive into the ground. This would keep your legs free to kick away until you swam too hard and pulled the stick out of the ground, and I would imagine if you were swimming hard enough the resistance bands (which are essentially giant rubber bands) would potentially launch the stick at you in the pool, hitting you in the head and knocking you unconscious so you drown. Being dead is a great way to lose weight, probably the fastest way.
Like most people who bought this piece of crap as an impulse purchase, my friend was not using it at his house and it basically just sat there next to his pool. According to him it would fail so frequently that you spent 75% of the time setting it up and re-attaching it when it invariably failed and 25% of the time actually swimming. Also, he said that even when it did work (briefly) the swimming felt very unnatural and he grew tired of it very quickly.
In situations like the one above where the pool is too small to actually do any sorts of laps I suppose I can understand why someone would be interested in something like this. However, if you have access to a gym or body of water, there is no substitute for the real thing. Professional swimmers other than the ones that were paid to promote these swim systems universally had negative things to say about it.
These days, even if you search online it is very difficult to find one that is even for sale and this is probably a good thing. If you do ever feel like testing this sort of portable swim system out do yourself a favor and go buy a metal fence post and some rope for around $4. That way, when it doesn't work and you feel like a jackass for even trying it, at least these things have some other purpose.