Wow:
> Strel swam the Amazon River, commencing on 1 February 2007, finishing 66 days later on April 7, 2007. This was a record-breaking distance of 5,268 kilometres (3,273 mi), longer than the width of the Atlantic Ocean. He had escort boats that were prepared to pour blood into the river to distract meat-eating fish such as piranhas.
https://en.m.wikipedia.org/wiki/Martin_Strel