Try aqua aerobics.

“This simple one hour class in the water has been a game changer. Since pregnant women have very few options when it comes to pain management, I have found aqua aerobics to be the one way to get any sort of real lasting relief. If I'm able to attend class regularly, about 3 times a week, I hardly have any tailbone pain after sitting in an office all day. My hips and lowerback feel better. [...] The weightlessness and sudden weight relief off my back while in the pool is the best after a long day.”

“I went to aqua aerobics for the first time the other day, and whilst I did enjoy it, I felt like I did most of it wrong. Most of it felt much too easy (which I don’t think it should have been, I’m v unfit!) and most of it was just turning around and walking. Up until we started using weights and pool noodles I didn’t feel any affect whatsoever on my body, and I felt clumsy and like I hadn’t grasped the concept.”