Players may assist each other in certain ways, by Trade or in Combat with enemies On Deck.
The way a player can assist another player in combat with enemies On Deck is by firing Artillery at enemies On Deck. This works mostly as an attack on an enemy ship, but the damage is handled differently: each point of successful damage causes 1 Trauma to one On Deck enemy on the targeted ship; the players choose which enemy, if there is more than one; but any blank results rolled on the Attack dice causes damage to the ship, in the same way that an enemy ship's attack would.
Trade
During a player's Turn, if the player's ship is on a space adjacent to another player's ship, they may by mutual agreement Trade; freely exchanging any number of Crew members, coins, Treasures, Schematics and Clues.