Along the same lines, a common myth about hot tub and pool sex is that a woman cannot get pregnant since she is in the water. The fact is that nothing in water can kill sperm or prevent pregnancy. Basically, once sperm have been ejaculated into the vagina, their goal is to find an egg to fertilize, and water will not stop this mission. This means that some type of birth control should be used.
Another myth about hot tub sex is that it is safe because the tub's heat kills sperm. This is not the case. Although being in a hot tub for more than 30 minutes may slightly lower sperm count, it does not decrease the number of sperm to a “safe” amount. Even with the lower sperm count, a man can still ejaculate 200 to 500 million healthy sperm –- and it only takes one to fertilize an egg.
Finally, although condoms do protect against both pregnancy and sexually transmitted infections, they are a risky birth control method to use during pool sex or hot tub sex. They can possibly rupture from decreased lubrication and possibly deteriorate from heat, chlorine, or oil-based substances in the water (i.e., tanning lotion, sun screen, bubble bath, etc). Plus, there is the added threat that the condom can slip off if water gets into it, and a man may be unaware of this happening. Also, keep in mind that although hormonal methods of birth control (like the pill, NuvaRing, Mirena IUD, and the Ortho Evra Patch) may provide pregnancy protection, these methods will not defend against any sexually transmitted diseases that can still be spread during water sex.