You can collect your rewards after the regatta finishes. Tap the chest in the bottom-right corner of the Tasks tab to open the Rewards window. It will display open chests that your co-op earned during the race and which you can now collect. Tap the screen to collect your reward. You must do it before the next regatta ends.
There are four types of chests: wooden, iron, golden, and precious.
The higher the league, the better your chances are of getting the most valuable chests during seasonal regattas.
IMPORTANT: if you leave your co-op before the regatta finishes, you will lose the chests you've received. That is why we recommend that you switch co-ops during the one-day break between regattas.
Apart from chests, you can collect the reward for your co-op's race position in seasonal regattas in the Race tab.