Okay, when you can't count on character or other 'noble' factors, get in touch with your inner sociopath and take another look at the situation.
2 Fully vaccinated guys, Bob and Jack, land on Bonaire, get the 'test at your resort' test, each goes to a private apartment rented for solo stay, and both test positive for COVID-19 (both remain asymptomatic). Well, crap. Now what?
Bob calls it in. Presumably his 10-day quarantine period (any way to shorten that?) starts immediately, that day? Or does it start with some sort of confirmatory follow up test? If Bob planned a 7-day stay, he's got to reschedule his flight. Which might even make him add more days than a 10-day total. If Bob's there 2-weeks, maybe after his 10-days he can cram in 3 days or so of diving? In Bonaire, you might 13 dives or so in that.
Jack, on the other hand, decides not to report it. He figures he can largely avoid people, wear a mask what little he's around others, and solo shore dive. He knows he'll probably get caught by the required Day 5 test, but figures that's 4 or 5 days diving he'll get it before they stop him.
But now Jack's 10-day quarantine starts 5 days into his trip, which will extend his stay well beyond what he planned, meaning extra costs, yes?
My point is, from a perspective of sole self-interest, is it in the diver traveler's best interest to report that first day + test, or wait to get caught by the day 5 test?