On the exterior of a hull); LIFERAFT (S. Refuge after capsizing [2 wds.]); UNDERWATER (T. Of an aquanaut’s milieu); MASTHEAD (U. Spot near a crow’s-nest); BEAUFORT (V. Eponym of a wind-strength scale); UNTIED (W. No longer having a mooring); SEASIDE (X. Typical locale for a summer resort). This acrostic is a