I've seen the morbidly obese in water aerobics classes; my mother was among that group, as a matter of fact. But I've suspected that swimming would actually be more effective for weight loss.
I got some support for my belief watching A&E's show, Heavy.
I know I've shared my mother's story here and at my personal blog
I used to watch Richard Simmons and sob, wishing my mother would participate. Now that she's gone, I obsess over shows like Heavy and The Biggest Loser, desperately wishing they could have saved her.
In the second episode of Heavy, I watched a young woman learn to swim for the first time at the age of 28, and weighing over 280 pounds. She had started out doing water aerobics, but once she learned to swim, her weight loss accelerated, and it gave her such hope.
Her partner in weight loss was not allowed in the pool at first because of an open sore on his leg. He was so happy when finally allowed into the pool. The 500+ pound man already knew how to swim, and he also accelerated his weight loss once he started swimming.
There is hope for the morbidly obese. Swimming is a lot gentler on their joints than land exercising. Don't ever give up. There are family members and friends who would miss you so much if you lose the fight.