Too much? How much?

I am moving somewhere where I won't be able to swim much for two years. Anyway, I made it my goal to swim 15,000 meters straight in four hours. I was only able to swim 14,000 meters, but it was a great experience. I actually had time to finish another thousand, but my body died on me. I should also say that I have not been training like I usually do, so this was a lot of swimming. It was a great accomplishment and I can now go without swimming for awhile. My question is, what is the most you have ever done in a workout or in a day and what has it meant to you? In my case, this was the most I had ever done in a workout. Most in a day was 25,000 that was stretched over the entire day. The meaning of my 14,000 meters was that I was able to have the mental and physical ability to handle doing this many meters by myself.