Think your local public pool is packed in the summer? We bet it's nothing compared to the world's most crowded pools.

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We'll start in Tokyo, where the Summerland resort boasts the biggest wave pool on earth.

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Dubbed 'The Great Journey', according to Time Out Tokyo, the 650 meter pool keeps throngs of people cool with well-timed waves that send them bobbing up and down, undoubtedly rubbing elbows with their neighbors.

Photojournalist Michael Yamashita has a series of photos from Summerland. He tells MyModernMet that most Americans are instantly grossed out by the photos, assuming the water is full of nasty bacteria.

But Yamashita says the The Great Journey is quite the opposite.

"Japanese people, by tradition and habit, are arguably the cleanest - not to mention the most cleanliness-conscious - in the world," he says. "The water in these pools is clean enough to drink."

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The reputation isn't as squeaky clean at China's network of massive public pools.

The Inquisitor reports China's Health Ministry found about 10-percent of the country's public pools exceeded acceptable levels for urea, a substance found in urine.

U.S. public pools don't get fantastic reviews, either. In 2008, the CDC says 12 percent of routine pool inspections found "serious violations that threatened public health and safety." Offending facilities were immediately closed until they met standards.

If thoughts of hitting a public pool make your stomach churn after reading those delightful stats, the CDC offers this advice:

• Avoid swallowing pool water or even getting it in your mouth.
• Shower before you get in the pool.
• Wash your hands after going to the bathroom or changing diapers.
• Ask the pool staff specific questions about how often the pool is treated.

You can find more helpful hints on the CDC website.

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