How do you cross rivers in AC: New Horizons?

Having just started a new game, some areas of my island are inaccessible, blocked by rivers I cannot cross. I assume eventually I will be able to construct bridges, but can I use anything else before then?

What are all the ways I can use to get on the other side of rivers, and are any of them permanent? Additionally, how can I unlock them?

Solution 1:

The first way is to use the Vaulting Pole.

This is from Blathers in the museum after you give him 15 donations (20 total). He only shows up after providing Tom Nook with the first five of those fauna.

You can also build bridges.

After Resident Services is upgraded from its tent form, you can build infrastructure. Bridge options include wood, iron, brick, suspension. And then you choose where it's built.