I am not convinced the vertigo is an issue with swimmers ear, people affected by that will also be affected in a pool. Our brains are designed to understand our orientation by the horizon. When you are in open water the horizon can be obscured by waves which means while are you are in it, you are fine, once you get back on dry land you are out of whack. In a pool the lanes and side of the pool are always easily in sight. This is a principle of flying IFR (instrument flight rules), if you are in a cloud you don’t have reference to a natural horizon so the plane could be 90 degrees or totally upside down and you may not be able to detect it. When you are trained as an open water lifeguard, this is also taught. Swimmers will panic when they can’t see land and will often start swimming *away *from land as opposed to towards it because they become disoriented.
i’m going with this. i swim in the caribbean (which is quite warm) and i am always a little dizzy and unsteady on my feet getting out of teh water and walking up the beach. by the time i’ve walked up to where my stuff is i’m back to normal. definitely NOT a cold water issue. when i swim in teh pool (much colder than the sea) i do not come out dizzy