Aut cum scuto aut in scuto
JMSDF Haruship-class diesel boat. Looks like she is doing 20 knots or so. Very nice
Highly inefficient bow wave. Modern subs don't belong on the surface. Dive, dive, dive!
Fully surfaced is the only way that submarine will go that fast for a transit. Running at periscope depth on snorkel or deep on battery won't be as fast.
Now hear this: Day watch personnel. Lay to the sail with Smartphones and selfie sticks.
The bow wave is even more impressive when you're standing in the sail, like those sailors, which I've done many times in the past.
I never got tired of watching the porpoises and flying fish jumping out of the bow wave.