I am looking for anyone with Judging experience. I race in the river and rule 19.C comes into play all the time.

"While boats are passing a continuing obstruction, if a boat that was clear astern and required to keep clear becomes overlapped between the other boat and the obstruction and, at the moment the overlap begins, there is not room for her to pass between them, she is not entitled to room under rule 19.2(b). While the boats remain overlapped, she shall keep clear and rules 10 and 11 do not apply.”

Does this mean at the moment of overlap you must have room between the boat and the obstruction after overlap you can call for water, or you must have room to pass the boat requiring you both boats to hold course during the length of the obstruction?