Sportech
Almost four years ago I started paddling va’a before dawn in Rio de Janeiro, and from the inside I learned how va’a, rowing, kayak and other water sports clubs work. Coaches organize the sessions on the water, athletes sign up for each one, boats have a set number of seats, and the sea decides whether anyone goes out. In the clubs I know, almost everything runs through a WhatsApp group, on a list that each person copies and pastes to sign up; in the two I studied closely, 83% of messages were those copies. There are apps built for this, one of them made by a paddler, and WhatsApp has polls and events, but neither of those two clubs uses them.
1 in 3Long breaks with no return
- Problem
- In a sport that gets you out of bed before dawn, the hard part is consistency. At that hour your head only wants to rest, and once the early enthusiasm wears off people start missing sessions, until one day they stop showing up. I’ve seen it many times at the club. In the groups I analyzed, one in three regulars who takes a long break never comes back.
- What I did
- What keeps someone in a sport like this is the group. In a meta-analysis by Carron, Hausenblas and Mack (1996), group cohesion is among what weighs most in whether people keep training, and people hold on longer when their effort counts for others, known as the Köhler effect. So Maré works inside the WhatsApp group. Existing apps ask people to install something and move the conversation elsewhere; with Maré, the coach shares a link and each athlete opens it without installing anything or creating an account. There they confirm, see who else is going and what the sea will be like hour by hour at the launch spot, which none of those apps show. If someone drops out, the next person on the waiting list gets the seat. Maré counts, reminds and keeps the record; the coach decides whether the session goes out.
Who’s going
The sea, hour by hour
Their sessions
Athlete app, with test data - Result
- In pilot with a va’a club in Rio since September 2026. The coach has already asked to add monthly fees. Now the pilot measures how many regulars who stopped coming 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: 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. Talking it through with the coach, we understood why: missing one morning and leaving the club are the same decision, the one that saves energy, and what turns it around is looking at the sea and knowing the group is waiting for you.
The group stays, because it holds the club together: one coach tried to close it and had to reopen 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 September 2026, the channels changed, from messages in the group to a personal link for each athlete, 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 water sport with recurring sessions, a fixed number of seats, one coach and a sea that decides whether the session goes out, from dragon boat and surfski to sailing and open-water swimming.