BLUF: Has anyone had experience using a swim harness/tether and can offer feedback or recommendations?

I will be going to Los Angeles in a few weeks and staying for a week at my in-laws, who have a small, backyard pool. I have a base of swimming fitness I would like to maintain as much as possible during the week. I have seen several swimming tether products that will allow you to "swim" in such a pool.

Has anyone tried a swim tether and can offer a recommendation or alternative?

Thanks in advance.