Group Rowing Classes

I've been teaching group water rowing classes at a small private studio in Marylebone central London called Trinity Health Clubs. It's interesting that in the past when I have trained people one on one with rowing machines that they don't seem to enjoy it, however I've had completely the opposite with group classes. Everyone comments that they can't believe that they have rowed for a session lasting 45 minutes, whereas before I found it hard to keep people going for 10 minutes! I know some of this is down to the fact that people enjoy working out on water rowers much more than the traditional concept 2 rowers that are found in large gyms. I wondered whether anyone had uses water rowers too, and if there are any alternative machines that you use (such as the pacific rower) to the water rowers and what you make of them? I've not tried anything else and am interested in what results people have found! And if anyone is in central London and would like to come and join a class please email me via the studios website www.trinityhealthclubs.com