Continuity mistake: During the avalanche at sea rocks fall and splash the oarsmen, but the splashes disappear in the shots of Jason keeping his balance in the prow.
Revealing mistake: When the arrow hits Medea and Jason pulls it away from her back, she crouches and the prop pad where it was stuck protrudes.
Other mistake: When Jason unscrews Talos' heel blood spurts but 1) it never creates a puddle and 2) the blood jet disappears in the wide shots.
Continuity mistake: In the beginning, a man who can see into the future puts his hands into a bowl filled with ashes. His hands now are blackened with soot, except for a side-on shot, where his hands are clean, with only a small amount of soot on them.
Revealing mistake: When Talos grabs the Argo and sailors start to fall, they disappear in the wide angles, revealing the ship to be a model.
