I was at the birth of my sister's son Caleb last August. She wanted a water birth and after her labour was in full swing they put her in the birthing pool. She was so much more comfortable in there and could cope with her pain better (only downside is you can ONLY have gas and air). Unfortunately it went belly up and she wasn't dilating so she had to get out and go on a drip. That's the closest I know of anyone having a water birth.