Regarding the original "leftist" revolution (which actually gave birth to the term "left"), something I'd never heard of before: Via Wikipedia...

The drownings were carried out by cramming some 90 priests in a flat-bottomed craft under hatches, and drowning them in mid-stream after scuttling the boat at a signal given, followed by another in which some 138 persons suffered like "sentence of deportation"; of these drownings there are said to have been no fewer than 25.

It is not certain exactly how many people Jean-Baptiste Carrier had executed in this manner. While it is popularly believed that around 2000 died in the Loire estuary, one member of Carrier's committee placed the number at over 6000.

One of the gruesome features of the noyades were what have been termed the 'underwater marriages', where a priest and a nun would be tied together before they were drowned. The drownings were also referred to as 'republican baptisms' or republican marriages.