Any sub firing a torpedo or shooting it's deck gun at another vessel is being attacked by a submarine (or U-boat). The term "U-boat" is the writer's or speaker's way of trying to speak the way a German person would say submarine. A true German enthusiast will even go so far as to pronounce U-Boat as U-Boot or "Underseaboot."
uboat
The Uboat was a submarine made by the Germans
It was the German way of saying "submarine" which properly should be called a "submersible." It is a shortening of "unterseeboot" to just uboat.
885.853199999 metres
Short for Unterseeboot - literally Undersea boat
In World WarII, the germans named it a uboat
24 hours
UBoat
The u boat can dive 200 to 250feet deep
yes
How many knots u have in ur grassy butt
The Allies sunk German Uboats. Uboat, not you-boat. Uboats stand for Unterseeboot - undersea boat.