When it's a 50
When it's NOT a 50
In the case of a C2, the boat leaves the gate line without both paddlers' heads passing through.
If a C2 crew would have incurred a 50 penalty because only one of the two paddlers has passed through the gate ("split gate"), the paddler/crew can return, make a second attempt at the gate and "clear" the 50 provided that they did not pass through the gate line in the wrong direction and they have not touched or negotiated a following gate. Both paddlers' heads must pass through the gate in the new attempt, not just the one who didn't before!
If there was a touch on any pass, the touch penalty stands.