Traditionally, oysters are grown in mesh sacks supported on trestles which sit in tidal estuaries. The sacks are covered at high tide but exposed at low tide allowing them to be turned over by hand. Turning the sacks is important because it prevents oysters bunching inside the sack and ensures an even distribution of oxygen and nutrients when they are submerged.
Robert Graham of the Dundrum Bay Oyster Fishery realised that productivity and oyster quality could be improved if the oysters could be turned automatically. Jack worked with him to develop a submersible carousel which tumbled the oysters automatically using a float operated indexing mechanism that rotated an incubation drum through ninety degrees on each rise and fall of the tide.