I'll give it a go.

Both boats appear to begin tacking at same time (not sure about whether Starboard boat attempts "fake tack").

Yellow Port sees Starboard tacking and maintains port tack.

Starboard dismisses tacking and sails back onto starboard tack AND below proper course.

Yellow surprised by this move tries to sail astern of Starboard.

Collision occurs.


Me think Starboard violated

Rule 13 (while tacking as she went head to wind--sails luffing at 0:12 -- and therefore must stay clear of other boats)

Rule 16.1 (When a right-of-way boat changes course she shall give the other room to keep clear

Rule 16.2 (...port-tack boat is keeping clear by sailing to pass astern of starboard-tack boat, the starboard-tack boat shall not change course if as a result the port-tack boat would immediately need to change course to continue keeping clear).