The S3 semisubmerged ship concept consists basically of two parallel torpedo-like hulls, submerged to a depth of about two diameters and attached to an above-water platform by means of four vertical struts. Horizontal fins and control surfaces attached to the hulls provide dynamic stability and permit full automatic control over pitch, heave, and roll. The anticipated advantages of the S3 over conventional ships are greatly improved seaworthiness, high-speed potential, large internal volume and deck area, controllability, and many aspects of its unusual hydrodynamic form. The S3 concept appears to be most applicable to small ships (100 to 15,000 tons) having missions associated with the use of sonar—the handling of aircraft, weapons, or submersibles—and for missions requiring a high degree of seaworthiness and stability.