I got a Halo swim bench last year after reading Sheila Taormina's Swim Speed Secrets book. I have poor swim technique and found the swim bench to be a really good way (for me) to focus on early vertical forearm and finishing the stroke all the way to the end while not having to think about everything else going on when in the pool (in addition to the strength training benefit.) Felt like it directly helped my stroke (and my awareness of the stroke) in the pool - but still have a long way to go to improve my swimming.

I've had one for years. I only use it in certain situations, but it is great at what it is designed for.
The biggest thing is that it allows you to use swim stretch cords without standing in a deep squat and blowing out your legs which are typically already cooked from cycling and running.
The bench allows you lay prone, with your head supported and your face exposed. This puts you in a neutral spine position.
Additionally the bench is narrow (as compared to something like a massage table) which allows you to move your arms through the swim stroke. The bench is also slightly inclined (in contrast to a strength training bench which is narrow but typically flat and doesn't have the head support).
The stretch cords have good handles that secure to your hands (across the knuckles on the palmar side of your hand) so that you can position your hands as if you were swimming. And they come in different resistances.
I use it without the HALO, but the HALO is a really helpful cue for people who would otherwise drop their elbow in the catch.
I use it to coach athletes on technique (high elbow in catch, complete finish, and extension in the front).
I use it for myself when I can't get to the pool. Not so much for a swim workout, but just to get moving and still replicate the swim range of motion and muscular activation.
I also use the cords to do standing chest press, standing row, bicep curl, and tricep extension.
You can mix it up high rep with the lighter cord, free, fly, low rep with the heavier cord, and even kneeling on the bench as if you were paddle boarding (surf rescue event). Super slow, work the catch, work the finish. Lots of options.