I found a French version of the quote on histoire-genealogie.com, where it was attributed to Plato:
« Il y a trois sortes d’hommes : les vivants, les morts, et ceux qui vont en mer » (Platon : Critias, L’Atlantide)
However, I could not find anything similar in a French translation of Critias, nor in a French translation of Timaeus (Plato's other dialogue that discusses Atlantis).
The quote may be a misrepresentation of something Diogenes Laertius wrote about Anacharsis in Lives of the Eminent Philosophers, more specifically, the following (in the translation by Robert Drew Hicks):
When some one inquired which were more in number, the living or the dead, he rejoined, "In which category, then, do you place those who are on the seas?"
Anacharsis was a Scythian philosopher who visited Athens around 589 BC, i.e. more than 150 years before Plato was born and roughly 200 years before Aristotle was born. Diogenes Laërtius lived in the third century AD; his Lives of the Eminent Philosophers also contains biographies of Plato (Book III) and Aristotle (in Book V).