It should be noted that the entire story of Jason and the Argonauts is essentially a story of cooperation and camaraderie, given that Jason needs to rely on his crewmates to retrieve the Golden Fleece in the first place. This is not a quest he can complete on his own, but one which is is reliant on the aid and assistance of other heroes.
With that in mind, perhaps one of the most striking episodes within these adventures involves the Symplegades, two enormous rocks that crash against each other, destroying any ships that try to brave the passage. In the story of Jason and the Argonauts, the crew of the Argo braves these rocks, sending a dove to fly through the passage, and in the aftermath, trying to race between the rocks as swiftly as possible. Even making this attempt would have required an extraordinary degree of synchronization and cooperation between the various crew members—though they still required divine intervention to make it through the passage.
Another famous adventure, found much later in the story, involves the sirens (famous for their appearance in the Odyssey). In the Golden Fleece story, Orpheus, the finest musician in Greece, plays a key role in the Argonauts' success, playing his own music to counter the beguiling effect of the sirens and allowing the Argonauts to pass safely through. These are only a few examples by which you can see the theme of cooperation expressed. A deeper read will reveal a great many more.