Sportech
Rowing and canoe clubs in Rio de Janeiro, where I row at 5:40 in the morning. A club is one coach, forty rowers, boats with a fixed number of seats and a sea that decides whether anyone goes out. It all runs through the group chat, because that’s where everyone already is.
6 hMedian wait for quorum1 in 3Long breaks with no return
- Problem
- The list fills to 95% and people still don’t show up. The group records who says they’ll come, never who got in the boat, so the coach can’t tell whether a session will go out, who is coming, or which regulars are drifting away.
- What I did
- Mapped the club’s day from 9,000 messages and redesigned it as a process with clear owners. The list opens at noon, whoever hasn’t answered gets a reminder, the waiting list moves up on its own, and the session closes with the sea forecast and the plan. Maré counts, reminds and keeps the record; the coach decides.
- List opens
- Reminder to whoever hasn’t answered
- Closing and the sea call
- Boat goes out
- Attendance marked
Maré runs itThe coach decidesThe waiting list moves up on its own - Result
- In pilot in Rio since October 2026, with the daily cycle running on Maré. Next, the pilot measures time to quorum and how many quiet regulars come back.
Read the full case
I started from a hypothesis about performance: the coach couldn’t tell whether the crew had improved or the sea had been kinder. I parsed 9,000 messages from clubs in Rio before building anything: 83% were copies of the list, and 30% of cycles lost confirmations when two people pasted at once. I corrected my own occupancy number when it didn’t match the club’s prices: the boats ran at 95%, with a waiting list half the days, so filling seats wasn’t what the coach needed.
Three facts seemed to contradict each other: lists fill all year, attendance drops in winter, and the coach complained about no-shows without a single number. They fit once you see that the group records intention and never who got in the boat. 67 times, a rower dropped out less than two hours before a 5:40 session, and lists took a median of 6 hours to reach quorum, so the coach spends every afternoon on watch. 13 of 39 long breaks among regulars had no return, one of them a rower with 51 confirmations, and the departures were sudden. The coach lacks control over whether the session goes out, who comes and who is leaving.
The group stays, because it holds the club together: one coach tried to close it and had to reopen it, the clubs I studied don’t use the app built to replace it, and in Rio a stolen phone takes every app and account with it. So the work went into the process around the group: who opens the list, what moves on its own, when the coach gets the sea call to approve, how attendance gets marked, and how leaving is measured per person, since changing schedule isn’t quitting. During the pilot, which started in October 2026, the channels changed, from messages in the group to a personal link for each rower, and the coach asked to bring monthly fees into the same cycle. Three rules held: the coach approves, the sea call is never automated, and money stays out of the group.
List apps already exist by the dozen, some of them free. The process fits any activity with recurring sessions, a fixed number of seats, one organizer and a condition that decides whether the session happens, such as kayak, SUP, sailing and diving, and the sea layer carries over whole.