can someone tell me why water won't go in a tampon when you are swimming with one?

it should go up and the tampon would hold your attention the water right?
Answers:

Water will stir into a tampon when swimming with one, like peas in a pod as water will turn into your vagina when swimming when not on your period, the tampons later absorb the pool marine to some degree.

Does anyone else hold frequent urination before getting their period?

Not really. It depends on the size of your vaginal opening and the size of the tampon. You might inevitability to change it for a time more often when swimming but it's not a big settlement.

Can you pregnant if you do anul sex?

Water WILL use the string as a wick. But like putting your cranium under hose down with your mouth closed - You will not bring much water up you snout as long as you don't do something to force the positive air pressure from your nostrils - close to inhale or exhale or pinch and release your nose.