Let's run through these. All statements are from the perspective of the Ghosts of Saltmarsh Appendix. All statements are sourced from a comparison of the UA Article and the Ghosts of Saltmarsh Appendix A
Action Economy has been Changed
In the UA, on its turn a ship could Move its speed and fire all weapons--or half of its weapons (rounded down) if the ship was at half-crew or less. They didn't really have Actions apart from "move and shoot every round."
In Ghosts, a ship can take multiple Actions per turn, dependent on how fully staffed it is. For example, a Galley (max crew 80) may take 3 actions--2 if at 40 crew or less, 1 if at 20 crew or less, and 0 if depleted to 3 crewmen or less.
Movement (Yes, Moving is now an Action for ships), and each discrete type of weapon the ship has consumes an Action to use. Each action option may only be used once per turn. So you cannot move multiple times or fire the same weapon set multiple times.
In general, a ship with a full crew has enough Actions to Move and Fire all of its weapons in a single turn. However, crew losses will force you to start choosing between your available actions
There are no official stats for an Airship
Those were in the UA article, they are not in Ghosts.
Maps and Descriptions
Saltmarsh added sample maps for ships, as well as detailed descriptions of said maps, with expanded descriptions of each type of ship beyond what is in the PHB.
Superior Ship Items
Effectively Magic Items for ships...Ghosts added these.
Officer Action renamed
UA called it 'Fire at Will,' Ghosts calls it 'Take Aim.'
Rules added for Crew Casualties in combat
Mostly guidelines on how to adjudicate what happens if someone Fireballs the deck of your ship.
Downtime Activity: Managing a Ship removed
It's gone. No trace of it in Ghosts.
Altered Hazard Rules
Hazard rules were condensed and heavily altered. The generic 'Everyone rolls for a hazard and adds their results together' Hazard rules are removed. Instead, there are a total of 5 Hazards listed that can occur, each with their own set of outcomes depending on success or failure.
Each hazard lists which specific officers are able to contribute to resolving the issue. Each eligible officer, along with the Crew as a whole, participates in a group check against a variable DC to determine how well they handled the crisis. There are 4 possible outcomes: Total Success (every die rolled generated a Success), Success (More or equal Succeeded than Failed), Failure (More Failed than Succeeded), and Total Failure (All dice rolls failed)
- Info and Encounter Tables for special environments, such as blue holes and coral reefs
- Random Ship Generator
- Random Mysterious Island Generator
- 3 sample underwater locations with maps.