Re: Overlooked Problem? / submarines
"Which is why modern, non-nuke subs use fuel cells. Diesel-electric is so 21st century."
They still are Diesel-electric but effectively with bigger batteries that are not charged by the engine but must be recharged at a shore base. And electric power is still very limited - hundreds rather than thousands of horsepower. There's also the vulnerability of hydrogen and oxidiser being stored outside the pressure hull.
Fortunately for world security, the technology doesn't yet exist to build an ideal stealth submarine.