What is the “misadventure” that William Douglas speaks about?

William Douglas had a “misadventure” when He was learning to swim in the Y.M.C.A. swimming pool. He went to the pool when no one else was there. But, He was timid about going in there alone so He was waiting for others to join in. A well-built boy threw him into the pool. At first, Douglas was frightened but he was confident. He tried his best to come out but his efforts made little difference. He was suffocating. He felt that the water was pulling him under. His legs and arms wouldn’t move. He tried to call for help but He couldn’t. He fainted at the end despite of all the efforts that He made.