Be warned right up front: When it comes to cruise ship pools, this story might make you say, “Gross!” or just nod and think, “Makes sense.”
Back in 2017, a University of Alberta study estimated that the average public pool contains around 20 gallons of urine.
That figure made headlines everywhere from The Doctors to NPR. The good news is that number referred to a massive 220,000-gallon commercial pool.
In comparison, a more typical pool, such as a residential one measuring 20 by 40 feet with a 5-foot depth, was estimated to contain only about 2 gallons of urine. That is considerably closer in size to most cruise ship pools, especially the ones on the lido deck.
So while the study focused on land-based pools, the question still floats to the surface: how clean are cruise ship pools, really?
Carnival Cruise Line says pool water is drained and reloaded a few times during each sailing. According to contributors on cruise forums like Quora, most ships still rely on filtered seawater, which passes through sand filters before filling the pools.
On many ships, the pool water is dumped daily in the early morning hours, the basin sanitized, and then refilled before guests even grab their morning coffee.
According to the Centers for Disease Control and Prevention’s Vessel Sanitation Program (VSP), cruise ship pool water must be recirculated every four to six hours, depending on the type of pool and filtration system. That guideline is still in place today.
The VSP continues to be the gold standard for cruise sanitation inspections. Ships that visit U.S. ports are inspected twice a year with no advance notice.
In 2024, the average inspection score was 95.9. A few ships scored in the low 60s but corrected course during follow-up visits. These inspections evaluate food handling, medical facilities, and of course, pools and spas.
One update for 2025 involves private hot tubs, especially those on suite balconies. Between late 2022 and mid-2024, the CDC linked at least 12 cases of Legionnaires’ disease to these private whirlpools. Ten passengers were hospitalized.
Unlike public hot tubs, these often do not follow strict sanitation procedures. The CDC now encourages travelers to use test strips to check water quality before climbing in.
Norovirus remains the most common cruise-related illness. A new strain, labeled GII.17, caused a surge in outbreaks earlier this year. Although cruise lines continue to emphasize hand washing and sanitizer use, recent CDC staffing cuts have raised concerns about their ability to manage and investigate outbreaks efficiently.
The bottom line is that cruise ship pools in 2025 are still among the cleanest public swimming options at sea or on land. With regular water turnover, filtered seawater, and CDC oversight still in place, you can dive in with confidence.
