According to the International Triathlon Union, the first officially recorded race took place in California in 1974 - run, 5.3 miles; cycle, five miles; swim, 600 yards. Even in imperial units, I know that's longer than my race.
That first triathlon was different to today's swim-cycle-run structure, which makes sense for competitors like me. If I do succumb to the dreaded and seemingly inevitable cramp, better be it on my feet than in the ocean.
Triathlon grew rapidly in popularity worldwide, making its Olympic debut in Sydney in 2000, with a 1.5km swim, 40km bike and 10km run. That's five times longer than my race.
New Zealand has a proud triathlon history, owning one of each of the Olympic medals. The competition, rivalry and sportsmanship between blokes like Hamish Carter and Bevan Docherty has become a part of national sports lore. And triathlon has a strong following in Nelson - I am certainly not the only Nelson Mail employee facing the team triathlon challenge this weekend.
I have done my homework. Saturday's race is minor when compared with the real deal. I know I'll have at least a few others struggling alongside me.
None of it helps. I'm still worried.