When you hop in the bathtub, pool, or ocean, it may seem like your period totally stops while you're in the water. But why? We asked OB/GYN Sherry Ross, MD, if this long-held belief is actually true.

"You period does not stop [1] when you go into a body of water," she told POPSUGAR. "The hormonal effect on your uterus that brings on a period is unaffected by going into water."

However, Dr. Ross said there are other outside influences that can cause your period to stop [2], such as severe stress, travelling, and extreme weight loss (or weight gain). "But going into a pool, lake, or hot tub is not one of them."

That being said, you should definitely use a tampon or menstrual cup [3] when you're planning on going swimming or sitting in a hot tub, but not a pad. "Wearing a sanitary pad would be messy and spread bacteria into the body of water you are going into," Dr. Ross said.

She also recommends putting in a fresh tampon or clean menstrual cup before getting into the water and changing it when you get out. If you're going to be at the beach all day, for example, you can leave them in for six to eight hours.