Are submarines streamlined

Answer 1

Absolutely - the modern submarine's teardrop shaped hull is a direct result of R&D that eventually led to the design that virtually all modern submarines use today.

Cigar shaped hulls are also used, but like the teardrop hull, they also taper to some extent at the aft portion of the hull, in the Engineering spaces. This is to provide better water flow over the aft control surfaces (rudder and stabilizers). Submarines travel underwater much the same as airplanes do in air, and it is no coincidence they have similar hull shapes.

The result of the modern submarine hull shape allows it to go much faster underwater than it can on the surface (a lot faster). In the past (WWII, e.g.) submarines were essentially surface vessels that had a limited submergence capability, and as such, they were designed to run much faster on the surface than underwater. With the advent of Nuclear Power and hull design changes, the submarine was transformed into a weapons system that could quickly gain the tactical advantage over surface vessels by being able capitalize on the speed given by the hull design.