Drowning related however, the most known is this one (even got a wiki page, so it's really well known!) en.m.wikipedia.org/wiki/Robert_Boulin
But Choukri Ghanem also managed to drown himself in Vienna.
A related death was Albichari, a 37 yo dying of diabetes, and 6 years later, Bechir Saleh assassination attempt by a commando (with his bodyguard crew saving him), so the DGSE clearly have multiple ways of doing business.
If you agree is that it's not a suicide, opinions differ on whether it's government team that did it or the "SAC", a paramilitary group linked to the then ruling party, not an official secret service
But i've read that recently "https://www.amazon.fr/tueurs-R%C3%A9publique-Assassinats-op%..." and now i have to jump in when people talk about political assassination, even though i know almost nothing about the subject, and everything i know is so thin it should be disregarded anyway. As the memory fade, i will stop doing that. Sorry :/