Yellow and Blue are beam reaching on starboard tack in the pre-start with Yellow clear ahead and slightly to windward of Blue’s course line. Yellow releases her sail, and Blue creates an overlap to leeward, without either boat changing course. The separation between the boats is only a few centimetres. Yellow luffs to keep clear and there is immediate contact. Both boats Y-flag. What should the call be?

Penalize Blue. Blue obtains right of way as a result of Yellow reducing speed. While the change in speed is a consequence of an action by Yellow, an increase or decrease in speed is not in itself an 'action' within the meaning of the second part of rule 15.

Therefore, rule 15 applies when Blue acquires right of way. As Blue creates the overlap so close that Yellow has no possibility of keeping clear, Blue does not give Yellow room to keep clear and breaks rule 15.