The most common reason for water lodging in your ear is that there's wax, and the water is getting over the wax, but then just can't get out. So if you're having water repeatedly stuck in your ear, the first thing to do is visit with your physician, let them look in your ear, and be sure that there's no wax.
On occasion, there may be a benign growth in your ear, these are not common, but, water can be trapped behind these growths. And, again, visit with your physician and be sure there's nothing wrong. Having said this, however, there are a group of individuals in whom water doesn't seem to want to run out due just to the natural anatomical configuration of their ear.
What can be done for this is rather straight forward.
Buy some rubbing alcohol over the counter in a pharmacy, and put it in a little dropper bottle with an eye dropper, turn your head to the side, and put two to three drops of alcohol into your ear, and jiggle your ear and rub it around.
The alcohol will run into your ear, mix with the water, and cause it to evaporate, and magically relieve you of the symptom. However, if the alcohol causes any burning, or any discomfort, or any pain, you must seek medical attention immediately to be sure that nothing else is going on. And, in fact, I think if you're going to use the alcohol, you should be sure that your physician looks in your ear first to be sure that nothing else is going on.