Noyades

The term is “Noyades" (French, noyer, to drown.) A means of execution adopted by Carrier at Nantes. It refers to drowning as many people at once...they have even taken 90 or so priests, stuffing them in a flat-bottom water craft and then scuttling it so the boat sinks–water pours in and everyone screams and gasps for air. See Wiki for more. It doesn't have to be priests though when using this technique. They say that Nero, at the suggestion of Anicetus, drowned his mother in this same manner.
It happened during the “Reign of Terror” which was fifteen months after The French Revolution.
Those being drowned were considered to be enemies of The Revolution and the noyades were primarily used against the religious factions that upheld monarchy rule.
Jean Baptiste-Carrier, who was responsible for helping to set up the tribunals to punish enemies of The Revolution, is said to be responsible for drowning 2000 people under his own command alone. The condemned suffered further humiliation in that he had them tied to their “ships of doom” naked.
Lastly, the noyades spawned the term “underwater marriages.” This is where they would couple up a priest and a nun, tie them together and send them to their watery grave. “To death do us part” was very quick.
The drownings were also referred to as 'republican baptisms'