The Yellow Duckmarine 'Wacker Quacker II'.
Another Yellow Duckmarine is also used; goes by the name of 'Wacker Quacker I'.

Both are modified D.U.K.W.'s from World War II. DUKW's were designed as amphibious transport vehicles by Roderic Stephens of Sparkman and Stephens Inc., naval architects based in New York. They were to meet the need to move men and materials up the beach when no other facilities existed. They have always been affectionately referred to as ‘Ducks’ and were based around a G.M.C. CCKW 2.5ton 6x6 army truck. Production totalled over 21,000 during the war.

The Photograph above shows 'splashdown' of the Duck into Salthouse Dock, during a trip on the Yellow Duckmarine. Look here to see it afloat, and look here to see it coming ashore.