ALB launched at 2156 to 18ft Yacht aground on Maplin Sands, 2 pob. Southend L/B and rescue 163 also proceeding. On scene at 2240 and standing off in deep water, Southend L/B also standing off, Rescue 163 airlifting casualties from craft at this time. Once casualties safe onboard helicopter, ALB and Southend L/B released, ALB escorting Southend back to station, casualty craft left aground on sands. ALB returned to station and ready for service at 2357. SE 6.