why did douglas go to lake wentworth?

Douglas was determined to get over his fear of water. So he hired an instructor who taught him to swim. While learning he had overcome most of his fears, but he still had some doubts. He no longer wanted his life to succumb to his childhood trauma, so he wanted to get rid of it completely. So to check if he had overcome his terror, he went to the Lake and put his new found courage to test.Hope this helps :)