Open Water Swim in SF

In town on business and brought my wetsuit. Swam for an hour with a group @ Aquatic Park last night in SF. Pretty cool swimming with Alcatraz off in the distance.

The swim was awesome but reminded me how much I need to work on my form.

Hello :)  My name is Lisa.  I started swimming laps about 2 months ago.  I really love it and feel very greatful that I have finally found an exercise that I enjoy!  However I am getting weight loss surgery in October and I'm nervous about how things will change and what I need to do to make sure that I don't start losing muscle mass from not having enough calories for my swims.  Do you have any advise for me?   Do you know how long it will take after surgery before I am able to swim as much as I am now (1 hour 4 times a week).  Plus I do 2 one hour strength training workouts a week.  I would appreciate any information that you can give me!!!! 

Thank you!
Lisa