Snorkel valve

A method of operating a snorkel valve comprised in a deployable mast assembly having an air inlet port, the snorkel valve comprising:

• a valve body having:
• a tubular wall having an outer surface and an inner surface on the reverse side of the outer surface, the inner surface defining an inner bore;
• a valve inlet extending through the tubular wall to fluidly connect the outer surface and the inner bore;
• and a valve outlet in fluid communication with the inner bore, and
• a sleeve slidable within the said inner bore between a closed position in which it covers the said valve inlet to thereby inhibit water from flowing from the air inlet port into the inner bore through the valve inlet, and an open position in which at least a portion of the said valve inlet is uncovered by the sleeve to thereby allow air to flow from the air inlet port into the said inner bore through the said valve inlet,
• the method comprising:
• moving the sleeve to, or holding the sleeve in, the closed position responsive to a determination that at least a portion of the air inlet port is submerged below a water surface;
• and moving the sleeve to, or holding the sleeve in, the open position responsive to a determination that the air inlet port is above the said water surface.