Here's your inspiration for your first triathlon this weekend. The big dude in the photo weighs about 2000 pounds, yet is an excellent swimmer. You probably weigh somewhat less than that, so I expect you'll glide through the water. Now buffaloes are not good bikers, but man can they run . . . sometimes as fast as 40 mph. It may take you a while to get up to that speed, but you'll run well. What I'm getting at here is athleticism - you have the ability, so use it and go out and have fun. Be a buffalo . . . but not on the bike.
Note - Found this question on a website: "There are lots of animals who could beat the best human runner in a foot race. And most sea creatures could beat the fastest human swimmer. But if we took the bicycle part out of the Iron Man Triathlon, is there any one animal that could beat the best Iron Man athlete in both the running and swimming parts?"
Answers offered included cockroaches, polar bears, ducks, tigers, horses, dogs, and otters. All of these creatures would be short on endurance, but I know of one animal that is an endurance runner and swimmer that could give a human some competition, especially in the run - the buffalo. If a human beat him on the swim, a buffalo, with its amazing lung capacity and speed, would easily pass him on the run.