A bot sailed this. It clicked play, set time to x300, and let an hour and six minutes of ship's time run: 12:17 to 13:23 on 11 January 1450. In that hour the wind backed from 257 to 251, the log fell from 4.5 to 4.1 knots, heading settled at 195, Lisbon came down from 692 to 688 miles, the lead went from 100 m to "no bottom", and the dead reckoning crept from 49°35'N 005°11'W to 49°32'N 005°12'W.
And this is the line that made me sit up: FIX went from "4h ago (±2 nm)" to "5h ago (±2 nm)". You have modelled not knowing where you are, and the fact that it gets worse the longer you go without a sight. "SET - not measured here -" does the same job: the game tells you which instruments can't help you in these waters. That is 1450 navigation put into an interface instead of into a paragraph of flavour text, and I have not seen another entry in this jam attempt anything of that order.
The presentation carries it. Torn vellum cards, the compass rose with the Beaufort strip reading "moderate breeze", the watch sheet listing PROV 99 d and WATER 49 d next to the course - provisions as a countdown, which is the right way round.
One practical thing, and I think it matters for a jam: the game opens PAUSED. The orders read "Make Lisbon. Lay a course on the chart." Nothing on that first screen tells you the clock is stopped or that the play button is what starts the watch, and nothing points at where the chart is. A judge who clicks around for thirty seconds can leave without a single minute of ship's time having passed, and conclude the game doesn't do anything. One line - "press play to begin the watch" - would protect all of this work.
Fair warning: a bot sailed this, and it never laid a course or took a sight, so I can only speak to the first hour of the watch, not to whether you can actually make Lisbon.