This fleet was built around maximizing the number of possession crew available to a fleet, and to give your opponent the feeling of being swarmed by Ugandan Knuckles. Or, at least, that's how I imagine facing this fleet feels.
The submarines each hold the crew possession abilities, and Slipstream receives the only re-roll available to them, giving her around a 31% chance (I think) of successful possession each turn, and her companions, about 17% each. This combines to give around a hypothetical 64% chance of a successful possession between the three, if my math holds up.
The idea is to send your subs at L+S to swarm enemy warships that may try to take down your gold runner, Morning Star. They roll to make a possession each turn, stripping your opponents' well-armed ships of their crew over time. If your opponent fields a heavily crewed-up ship, laden with powerful abilities, this could be a strategy with which to counter that. Staying submerged means that the odds of your subs taking damage are minimal, and they can gang up to repeatedly ram their target to try to disable it. Once derelict, if your opponent doesn't scuttle the ship, you can keep trying to steal its crew. You can also just opt to leave it damaged enough that it doesn't try to engage Morning Star.
However, given this fleet's sole purpose of capitalizing on an expensive gimmick, there are a boatload (no wordplay here) of weaknesses with this proposed strategy.
- Gold rush fleets that can either canvas the game area better than or outrun Morning Star will win the game outright. This fleet's warships are meant to steal crew, not chase down fast gold ships.
- The effectiveness of ramming is increased against multiple small or midsized (2-3 mast) gunships, but it makes the crew possession ability next to useless, as they will be less stacked with crew.
- Dreadnoughts 6 masts and bigger are immune to ramming without prior damage, leaving just crew theft as an option, but it won't be so easy if your opponent deploys fast warships like San Cristobal or HMS Grand Temple.
- The strategy itself works rather slowly. Even if you're generous with the odds, only 2 crew are likely to be stolen every three turns.
- Before managing to steal a captain, this fleet is not at all equipped with such a crew, making surface engagements something to avoid.
- ASW ships would stand a chance of demolishing this fleet, provided the ship using the ability of crew like Shinji Smith are reasonably well-armed.
- Cancelers and the danger of the Fear and Parley keywords almost nullify this fleet's strengths entirely. The former two can force ships to surface against their will, and Parley can prevent the possession strategy from even being an option.
- Cursed Captain Jack can make every ship here surface, and move at a pathetic L, with no captains.
Overall, I bet this fleet will do nothing but flop, but it could prove an interesting way to lose a game. In an ideal scenario, you get to yank all the powerful cheesing crew from a 5, 6, or 10 master before surfacing to blow it out of the water, and then turning your focus on the remainder of your foe's fleet. This could probably work better if it were part of a larger fleet, but consideration of how to make that a reality will come later.