I was able to use one in our pool's dry land training room during a 2 week pool closure. I really liked it and wish I had access to one more often. Since the pool was closed at the time, I don't know if it helped my swimming or not but the exercise I felt from it was great.
A team I swam for one summer had a few. We used them as part of our dryland before we hopped in the pool. I liked them, helped stregthen my shoulders :cool: