Does this work only with a generic Explorer, or does anyone with the keyword count? Looking specifically at Dominic Freda from RotF (Explorer, +1 cargo, takes up no space), who thanks to the similar-but-technically-stackable wordings would give this ship +2 cargo while taking up none.
Silver Explorers have to be considered too, but they shouldn’t an issue either way.
It’s intended to function the same way an ability referencing a Captain does, so any generic explorer or any crew with an Explorer keyword.
Any restrictions on what it can fire at? This doesn’t override any abilities about shooting at submerged ships, so it would have to be assumed to only work against surface ships unless specifically stated otherwise.
What about a Marine on a island?
This ability is intended to indicate that the ship is able to fire a sort of early/primitive underwater torpedo, so in effect it would work mostly the same as a regular cannon. I had forgotten about marines, some clarifying text indicating they cannot be targeted is likely to be in order. With that as well as some clarifying text about submerged pieces (it shouldn’t be able to fire at them regardless of if an ability would allow it) I may end up turning it into a keyword to better abbreviate.