You can earn Boating credits by inviting your friends to sign up and complete a Qualifying Boat Rental. You can find your invite code and your invite link in your Profile tab>Settings>Referrals, or in the email received from Sailo.
The Boating credits accumulate and could be applied to the next Qualifying Boat Rental if user chooses to. If the boat rental price is higher than available credit, then all Boating credits will be used and the balance will be paid by credit card. If the boat rental price is lower than available credit, then only the needed credit will be used and the credit balance will be available for the next Qualifying Boat Rental.
Remember, personal invite codes should only be used for personal and noncommercial purposes. This means that you can share your invite link with your personal connections via personal email, Facebook or Twitter personal accounts, or by copying the code or invite link and sharing that using a method at your choice. Public distribution on sites where you are a contributor but not the primary content owner (e.g., Wikipedia, Reddit coupon websites) is not allowed. Promoting your referral code via Search Engine Marketing (e.g., AdWords/Yahoo/Bing) is also not allowed.