Imagine standing on the bank of a peaceful river. The water flows gently toward the sea. Birds chirp. It’s calm. Then, from the distance, a low rumble begins. The sound grows—like thunder rolling down a tunnel. And suddenly, a single, massive wave comes surging upriver, flipping direction like some ancient force just changed its mind. Welcome to the tidal bore of the Yatsushiro Sea.

If you’ve ever dreamed of swimming with jellyfish without turning into a human pincushion, your fantasy is not only possible—it’s floating in the heart of Indonesia.