We did a course.
I found it great for relaxing during pregnancy. The course itself was very helpful also in explainign why relaxing and breathing are so important and helpful.
If you're new to hypno stuff i wouldn't expect to be able to completely zone out (or in?) but it can still be very helpful in focusing your mind and helping you to remain calm. I see no reason you can't do that in the water either - probably be even easier that way.
The thing that worked best for me was even when the contractions were very intense and I didn't think I coudl do it anymore, I was able to put my head down adn breath and recover during the little breaks and gather myself for just one more.