Trapped against the shore
The situation
Two boats beat up a shoreline overlapped on starboard. Green is the leeward boat, close to the shore and running out of water; Blue is pinning her from windward. Green will run aground if she holds on.
The question
Green needs to tack to avoid the shore but Blue is in the way. What can she do?
The ruling
Green may hail “Room to tack!” Under rule 20 the hailed boat (Blue) must respond — either tack as soon as possible, or immediately reply “You tack.” She can't just ignore the hail. Here Blue tacks first to open room, then Green tacks behind her. While tacking, rule 13 still applies to both — neither has rights until back on a close-hauled course.
Trapped against an obstruction and need to tack? Hail “Room to tack” — the other boat must tack or tell you to.
Opens the situation on the boat-length grid — scrub it and see exactly how the boats meet. Free, no account needed.
Rules cited
See the underlying rule: Rule 20 — Room to Tack at an Obstruction.