I have never been a very good swimmer, preferring the sea to a pool. However, this problem hit me about three years ago when away on holiday. We went on a boat trip, and no I didn't jump overboard, but waited until we reached a lovely little bay.
Everyone went swimming and as it was so hot, I joined them. I was swimming around, not in deep water, when I decided to stand up but I couldn't get my legs down to stand up. The next thing I knew I was being rescued by the Captain of our boat, who towed me back to the beach. Not a toy boy by any stretch of the imagination - but who had noticed I was in trouble.
Since then I have always suffered the same problem and now only swim to the side of the pool where I can catch hold of the side to stand up. This means I am not able to swim in the sea. I just don't understand this difficulty and wondered if anyone could shed some light on it.