Tokens are a special currency you can get by completing seasonal regatta tasks. Go for complicated and season-themed tasks to earn more of them. Participating co-op members also get tokens once the seasonal race is over—the better the co-op finishes, the bigger the reward.
You need tokens to make purchases at the Yacht Club, which is the store for regatta participants. Tokens don't expire, and players can spend them whenever they want after the season is over, but the maximum amount of tokens is capped at 600.
The store is located next to the Pier. You can access it by tapping the ship icon in the Season tab as well.