I used to swim like crazy on holidays to maintain muscle tension when no gym nearby. Used very short interval sprints, chestcrawl, which involves a great deal of chest lats and arms also.
Tip: chestcrawl has breathing technique and cardiovascular condition as a limiting factor but if you use a scuba mask you can keep your head in the water for continuous breathing.
Do a short sprint, have active rest for 30-60 seconds by doing steady aquajogging and go at it again, repeat until you feel like you gonna sink as a stone to the bottom. than take 3 minutes rest , repeat two times....
Train like Jaws is chasing you! and do this everyday 2 times on holidays and I guarantee that your metabolism skyrockets and melt away fat, but you exercise most muscles with enough intensity to keep good size.
The best results I got when I combined the swimming sessions with 2 visits to the local gym, basically I was having 4 workouts a day, Actually I was eating all day like a crazy mofo and still my waistline kept shrinking. Mentally it is heavy though, sometimes you feel really beat up and about to go insane, you can reach a nice peak (good balance of size and BF) in the second week.
I couldn't possibly maintain this kind of renegade training for a whole year.