New dates from two sites on the Indonesian island of Flores prove that Homo erectus was able to navigate open waters between 800,000 and 900,000 years ago. Previously, modern humans who colonized Australia were credited with the earliest sea crossings, 40,000 to 60,000 years ago.
Source: First Mariners – Archaeology Magazine Archive
Tim B.
https://en.wikipedia.org/wiki/Mata_Menge
Tim B.
“Mata Menge
Fossil teeth and a partial jaw from hominins assumed to be ancestral to H. floresiensis were discovered in 2014 and described in 2016.[11] These remains are from a site on Flores called Mata Menge, about 74 km from Liang Bua. They date to about 700,000 years ago[12] and are even smaller than the later fossils.[13] ”
https://en.wikipedia.org/wiki/Homo_floresiensis