[ Just are Rin arrives, this little invitation falls into his hands. Normally a new arrival would need to time to settle and become familiar with their environment, but not Rin.
He doesn't have anything to worry about since the Usyagi assures him that his brother and friends are fine, and he doesn't sense anything menacing from the fluffballs. What better way to get to know this place than to interact with the other people here? That's how Rin justifies his enthusiasm to jump into a boat. If you ride with him, it surely won't be a quiet ride. Probing with questions and trying to get know you. He might also be rocking the boat during the conversation.
And probably something bad happens, and the boat capsizes halfway through the journey and you end up drenched once you make it to beach's shore. Good thing there's a bonfire to warm up.] My bad...