A couple of years ago I saw a crossfit games triple 3 workout that includes a rowing leg. It is a 3K row, 300 double under jump ropes, run three miles. This workout hinges on the jump rope skill / efficiency with that exercise will have the biggest impact on your time. First time I did it, it took me just under 45 minutes. I was fairly practiced with the jump rope. Since then I have gotten the time down close to 40 minutes. Mostly by getting more efficient at jumping rope.
Pain is inevitable, suffering is optional