Since you mention that you could cycle, it opens up the option to use an **amphibious bicycle**.

It would use flotation devices that fold down and outwards so that you can use it on the street as well with no issues, and covert it to amphib mode quickly (perhaps even with the push of a button). With the usual designs, your feet would go into the water when pedaling, so you would have to wear high waterproof trousers with attached boots (not the [chest high wading trousers][1] as in the other answer though). But since one side of your river has no easy way to get in and out and it will not be possible to drive the bicycle on muddy river ground, you need to unmount and walk the last few meters anyway – which means, you need these trousers anyway.

As for do-it-yourself designs to convert a normal bicycle into an amphib one, here are some inspirations from YouTube:

* [an amphib bicycle from India][2]
* [another amphib bicycle from India][3]
* [an amphib bicycle from somewhere else in Asia][4], rebuilt and tested by Mythbusters
* [a commercial kit for an amphib bicycle by an Italian company][5]


  [1]: https://lifehacks.stackexchange.com/a/20685
  [2]: https://www.youtube.com/watch?v=REx9rMDbqRg
  [3]: https://www.youtube.com/watch?v=T1BQZ7T9tqs
  [4]: https://www.youtube.com/watch?v=Z7YLWpnYfts
  [5]: https://www.youtube.com/watch?v=UIwGB-qQc6M