 The Baker shot produced so many unusual phenomena that a conference was held two months later to standardize nomenclature and define new terms for use in descriptions and analysis. The underwater fireball took the form of a rapidly expanding hot gas bubble that pushed against the water, generating a supersonic hydraulic shock wave which crushed the hulls of nearby ships as it spread out. Eventually it slowed to the speed of sound in water, which is one mile per second (1600 m / s), five times faster than that of sound in air. On the surface, the shock wave was visible as the leading edge of a rapidly expanding ring of dark water, called the "slick" for its resemblance to an oil slick. Close behind the slick was a visually more dramatic, but less destructive whitening of the water surface called the "crack".
