Nothing works for me. Counter-throw doesn't work, grabs don't work, running into them and knocking them into water doesn't work, tossing their dead bodies into the water doesn't work. So many stupid bugs in this game, and they're extremely unclear on how to do certain moves.
Hmm... when I did it, I was on the planks that connect the ships to the stone platforms. I definitely did the counter-throw, because I was trying everything (the same process you guys did), so when I noticed my counter going up, I did two more counter-throws and I was done.
"I dreamt that I was a 'Genie-Firefighter'! I fought fires and granted wishes!"