In one of the 'Sneekweeks' I've been involved in, we had a protest involving the shore as an obstruction. Between two '16m2's - a Dutch national class 6 meter keel boat. (The 16 square meters is how much sail they have). No spinnaker and very popular because you can build them yourselves. (See photo below)
Anyway, Yellow and Blue approach the shore, to enter the Sybesloot connecting two parts of the lake. Blue hails for room to tack. Yellow response is: "You Tack" and continues sailing. Blue luffs but not as fast as she wants and clears the stern of Yellow when passing head-to-wind. Because she lost speed, ends up half a boat length lower than Yellow. Blue protests and puts up her red flag.
You're in the protestroom and hear the testimony from both sailors. Write the protest with facts found, conclusion and rules that apply and a decision.
Oh, in the original protest Blue categorically denied ever hearing Yellow's hail, but Yellow asserts she hailed loud and clear.