According to LiveScience columnist Sally Law there are several risks when it comes to the rather enjoyable topic of summer sex:
While condoms are meant to be compatible with water-based lubricants, they should not be completely submerged in water. Condom companies don’t test their products in such a condition, and therefore can’t vouch for their effectiveness when used in pools, hot tubs or other wet and wild setups.
But even for people in a monogamous relationship the conditions can be tricky:
You still might want to avoid water sex, as improperly maintained pools, hot tubs and Jacuzzis can be breeding grounds for bacteria. A study released last fall by Oregon State University found that summer is a bad time for bacterial infections in general, with serious infections caused by bacteria up as much as 17 percent with every 10-degree increase in seasonal air temperature.
I am not sure if the last mentioned danger is a risk or rather a bonus though:
A 2007 study conducted by the University of California, San Francisco, found that total body exposure to wet heat can impair both sperm production and motility. The study’s participants reported the use of a hot tub, heated Jacuzzi or bath at a temperature warmer than their body temperature for 30 minutes or more per week for at least three months prior to participation in the study.
Via LiveScience.