3721 mph, but that would be in a submarine, not on the surface, at sea
level, the nasa standard table puts SOS at sea level in daytime at
761mph...so that is what a surface vessel would have to achieve to
break the sound barrier; even a displacement hull is still floating on
the surface of th water, so it wold be subject to gas physics.A boat on
the surface is exerting a fixed force on the water (in a perfect
world), this force remains more or less constant, varying onle due to
lift and loss of it while moving, this will not generate a fast enough
shock wave through water to cause a "sonic boom"