What Happens to Semen in Water?

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  • Originally Written By: Erin J. Hill
  • Revised By: C. Mitchell
  • Edited By: Bronwyn Harris
  • Last Modified Date: 08 July 2019
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Semen is not typically impacted by water in the short term, which is to say that sperm will generally survive, at least at first. A lot depends on temperature as well as the amount of water present. In most men semen is itself made up primarily of water. Adding more will cause the mixture to become diluted, though depending on the specifics of the encounter the semen might actually gum up or become clumped at first if the water washes away some of the proteins responsible for keeping the mixture fluid. Extended water exposure may also lead to sperm breakdown over time. Sperm already have short lifespans, though. Sometimes warm water will actually prolong their life, but cold pools and puddles often have the opposite effect.

Semen Basics

The semen of humans and most animals is made up primarily of water — up to 90% by some estimates. From this perspective, nothing unusual happens to semen in water, since in most cases it is already basically there. Human semen is typically a combination of water, sperm, and proteins, though, and one of the main impacts of added water is an upset of this balance.

Sperm generally thrive best in water that is approximately body temperature, or 98.6°F (37°C). They can survive in water that is slightly warmer or slightly colder, but not always. In these cases, though, it’s the temperature more than the water that’s killing them off.


Some men also find that their semen tends to coagulate or become almost gelatinous in the water, particularly in the shower. This is usually due to the way the water is hitting the ejaculate and the response of certain proteins. Two of the most important proteins present control coagulating and de-coagulating, often as an evolutionary protection mechanism. It isn’t true for everyone, but in many cases the de-coagulating protein will wash away first, leaving a gum-like mass behind. Over time this, too, will dissolve and wash away, but it can be unsettling to see at first.

Consequences of Mixing

In nearly all cases water will slowly mix and combine with any fluids added to it, and semen is not usually any sort of exception. Semen tends to be thicker than water, so this may take several minutes or even longer to occur. A small amount of semen may be seen floating on the top of water for quite some time after ejaculation, or it may sink. The ability of semen to float may be related to the diet and lifestyle of the man since eating certain foods or engaging in certain activities may impact semen's consistency.

Consistency Issues

It should be obvious that watery semen will dilute with water more quickly than will thicker semen. Thicker semen is more likely to appear white and float above the surface, while clear, thinner, semen is most likely to sink. The temperature of the water may also make a difference here, as well.

Pregnancy and Disease Concerns

Some women may become worried about pregnancy should they encounter semen in water, particularly during sexual activities performed in a bathtub or hot tub. This is not typically a concern, but if continued sexual activities are engaged in, the risk may be higher. If pregnancy is a concern, then protection should be used even when engaging in foreplay in the tub, pool, or hot tub. Although sperm won't live very long in cold water, they may survive for up to a few hours in hot or warm water since they thrive in wet and warm environments. It isn’t usually easy to become impregnanted simply by being in close proximity to semen, but a woman who is already naked and aroused may run a greater risk.

Some communicable disease-related concerns over semen in water are also common. Human immunodeficiency virus (HIV) is a major health concern, and if infected semen comes in contact with an open wound, the disease may be spread. This is generally not a problem in places like swimming pools and hot tubs if the proper chemicals are used in the water for cleaning and disinfecting. Other areas may not be as safe, although the chances of transmission from waterborne semen are still relatively small.


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Post 4

This is such a weird thing for people to be worried about. Although I guess some couples like doing it in the hot tub and it would be difficult to practice safe sex in there.

If the pill isn't an option, you might want to look into other forms of birth control. I suspect if people are worried that semen is going into water, should also be cautious about it going elsewhere, since it obviously isn't going into a condom.

Post 3

@pastanaga - It probably depends on the situation. I mean, if it is a spa pool and the temperature is just right, I think it's much more likely. And, when it comes down to it, I think the risk of disease is much more dangerous, so it seems like the kind of thing you'd want to prevent if you can.

The whole thing just seems quite gross to me, to be honest. But anyone who has ever worked at a public pool has got to know those things are usually more bacteria than water, especially if kids play in them. I don't think they are dangerous, since there is so much chlorine, but it isn't nice to think about.

Post 2

I've heard all kinds of urban legends about this, where someone manages to become pregnant from a spa or swimming pool. It's usually either a family member's baby (which is completely sick, but urban legends usually are) or it happens at the local swimming pool and there's no way to know who the father is.

I don't believe that this has ever happened though. I mean, the odds of a sperm cell surviving long enough to make it to a woman and somehow managing to make it to an egg cell as well, even though they usually don't make it even when people are trying to get pregnant, just seem too impossible.

Maybe it's possible, but I doubt it has ever happened. If anyone claims otherwise I suspect they have a reason to lie about it.

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