An octuple scull is a racing shell

Racing shell

In watercraft, a racing shell is an extremely narrow, and often disproportionately long, rowing boat specifically designed for racing or exercise. It is outfitted with long oars, outriggers to hold the oarlocks away from the boat, and sliding seats...

 or a rowing boat used in the sport of competitive rowing

Rowing (sport)

Rowing is a sport in which athletes race against each other on rivers, on lakes or on the ocean, depending upon the type of race and the discipline. The boats are propelled by the reaction forces on the oar blades as they are pushed against the water...

. The octuple is directed by a coxswain

Coxswain (rowing)

In a crew, the coxswain is the member who sits in the stern facing the bow, steers the boat, and coordinates the power and rhythm of the rowers.- Role :The role of a coxswain within a crew is to:...

 and propelled by eight rowers who move the boat by sculling

Sculling

Sculling generally refers to a method of using oars to propel watercraft in which the oar or oars touch the water on both the port and starboard sides of the craft, or over the stern...

 with two oars

Oar (sport rowing)

In rowing, oars are used to propel the boat. Oars differ from paddles in that they use a fixed fulcrum to transfer power from the handle to the blade, rather than using the athlete's shoulders or hands as the pivot-point as in canoeing and kayaking. Typical Sculling oars are around 284 cm -...

, one in each hand. Like a coxed eight, an octuple is 65.2 feet long (19.9 meters) and weighs 211.2 pounds (96 kilograms).

Racing boats (often called "shells") are long, narrow, and broadly semi-circular in cross-section in order to reduce drag to a minimum. They usually have a fin towards the rear, to help prevent roll and yaw. Originally made from wood

Wood

Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

, shells are now almost always made from a composite material

Composite material

Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...

 (usually carbon-fibre reinforced plastic) for strength and weight advantages. The riggers in sculling apply the forces symmetrically to each side of the boat.

When there are eight rowers in a boat, each with only one sweep oar and rowing on opposite sides, the combination is referred to as a "coxed eight." In sweep oared racing the rigging means the forces are staggered alternately along the boat. The symmetrical forces in sculling make the boat more efficient and so the octuple scull is faster than the coxed eight.