A guy on here said he had a pair of gloves that did this back in the 90’s, but the “problem is you have to spread your fingers instead of pressing them together. Basically relearning to swim in order to be efficient with these. Can’t use them occasionally & expect them to do anything but cause frustration & fatigue.”
So they’re real training tools.
Some might wonder about pain in the joints and fingers after 2h of swimming, but people who’ve used them say you dont notice them, they will build muscle. So it’s more just the inconvenience.
There are also flat ‘plate’ ones.
Does it remind you of Patrick Duffy in the Man from Atlantis?
You can get these in small and full-hand versions.
Click the picture to see the products and how much they are: