How to Cross Rivers
To cross a river in New Horizons, you’ll need to build a Vaulting Pole. To craft a Vaulting Pole, you’ll need to acquire the recipe from a certain famous owl.
Early in the game, you’ll be asked to put down a tent for Blathers, who’s interested in the local fauna. The day after you’ve set-up Blathers’ tent, the owl museum curator will move to your island.
Speak to Blathers as soon as you can as they give you the crafting recipe for a Vaulting Pole and the all-important Flimsy Shovel.
Once you visit a crafting station, you’ll learn that you need five pieces of softwood to craft the Vaulting Pole. To get these, you’ll need to chop trees with your Axe (by pressing A against a tree). Doing so will produce one of three types of wood, with the lightest in color being the softwood.
With your Vaulting Pole in hand, all you have to do is approach the bank of a river, move in the direction that you want to vault, and then press A to cross rivers in Animal Crossing: New Horizons.