Aquanatal can reduce the need for pain relief in labour

In this randomized, controlled clinical trial, 34 pregnant women did water aerobics and 37 no specific exercise. There was no difference between the two groups in the duration of labour, type of delivery or birth outcomes. However, significantly fewer women in the water aerobics group requested pain relief (27% vs 65%). The regular practice of moderate water aerobics was safe for sedentary and low risk pregnant women. 

[Baciuk, EP and 4 others: Water aerobics in pregnancy: Cardiovascular response, labor and neonatal outcomes. Reprod Health. 2008 Nov 21;5:10.]