A rather unique mission post shows up one day on the job office. It calls for a group of shinobi to come to the aid of a village. The only requirements seem to be an ability to swim and MAYBE being paid in fish. Any potential participants were to meet with Guran Sarutobi.
After meeting up and a brief rundown, Guran lead the group to a massive river at the edge of the Land of Hotsprings. A simple series of Hand Seals opened the entrance in the river to an inverted world that held the village on the river bed and made the surface of the river it's sky. It would've been a beautiful sight had it not been for the fact that the village was decimated by a Naga attack.
Upon reaching the village, they were greeted by Chief Nemo and told of what happened. The village was recovering from an attack by a once long dead enemy and that the only way to end was to completely eradicate their nest and kill their queen. After much debate and a second attack they agreed and fought their way to the Queens lair.
Inside they faced off against a being only known as the Entity and won. In a last effort to even the fight, the being caved the roof of the room which only ended in potentially killing herself as the Genin party escaped.
After all was done and over with, Nemo Gabe everyone souvenir necklaces and made them official otterkin, members and heroes of his village. Not too shabby.