The DSEI show had someinteresting naval displays from BAE.

This is an 8000 ton (supercarriers are 75,000+ton) destroyer with a rear flight deck for dispatching UAVs. I’d call it more of a UAV tender than a Carrier.

This is a submarine propelled by 8 pumpjets mounted in the tail. It does away with the reduction gear of a direct drive system. If I recall correctly, the Seawolf and Virginia class boats use a single screw/pump with electric drive for much the same reason.

Those gears are heavy, very precise, and hence expensive, and (if anything goes wrong) noisy.

This is a mockup of an air independent propulsion system for submarines. As opposed to using a fuel cell, they are using a diesel generator, which promises to be cheaper.