Unlike Jules Verne's futuristic 'Nautilus' in the book 20000. Leagues under the Sea, a naval submarine does not have windows because you cannot see more than a few yards when under the sea.
Amazingly, a dived submarine operating deep under the sea has about a quarter of a million tonnes of seawater pressing on it all round. Any windows would demand highly expensive toughened glass and sealing but this would not withstand weapons attack.
A modern submarine, more than any other type of ship or engineered product, requires the highest class of workmanship on its hull and systems and this is what the shipyard at Barrow is famous for around the world.
Sightseeing 'submarines' becoming popular at holiday resorts have viewing windows but they are actually submersibles which only just go under the surface for brief periods and use powerful lights to attract marine life close enough to be seen.
