Just completed my first aquathlon (750m swim + 5km run) at Sentosa, and though I had prepared for this with open water swims and a self-organised triathlon at Oswald's place, some parts were surprisingly difficult.
Firstly, logistics occupied more mental space than I expected. The preparation, the transition, and the little things I brought to keep me comfortable all added up. I remember fumbling to put on my safety pin on my running shirt while I was figuring out whether the little strap they provided me was an ankle tag or bib belt (it was the number tag). All this while under the beaming sun, with not more than a few minutes to the starting time. There was also some mental gymnastics about mask wearing, as we had to put on our masks immediately before and after the race, but we couldn't return to the start point, so we had to dispose of our prior masks and get new ones at the end.
Secondly, the swim was much tougher when you're swarmed by competitors. People arming into my lane, my legs, blocking my view. It was so bad that I actually visualised giving up 25% into the swim, after gulping a mouthful of seawater.
Anyhow, I fell back the swimming pack to have my own space, and regained my composure. From there on, things went more swimmingly. I must say hearing cheers around you really does boost the morale. And the whole day of manufactured hardship did make my Sunday sleep that much sweeter.