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Glossary of seaplane terms

Plain definitions for the words you will see on seaplane base pages, in pilot conversation, and in aviation publications. Each term links directly — share or bookmark any definition.

AMES

Airplane multi-engine sea. An FAA class rating that allows a pilot to fly multi-engine seaplanes. Requires a practical flight test in a multi-engine seaplane.

Amphibian

A seaplane — either a floatplane or a flying boat — equipped with retractable landing gear, allowing it to operate from both water and paved runways.

ASES

Airplane single-engine sea. An FAA class rating that allows a pilot to fly single-engine seaplanes. The most common seaplane rating, typically earned in a float-equipped Cessna or Piper.

Beaching

Bringing a floatplane to shore and securing it on a beach or riverbank, rather than at a dock. The pilot taxis to shallow water and lets the floats touch bottom or ground on sand or gravel.

Density altitude

Pressure altitude corrected for temperature. High density altitude means the air is thinner, reducing engine power and wing lift. Seaplanes are especially affected because water takeoff runs are already longer than runway takeoffs. Shown on waterdrome.com base pages when METAR data is available.

Displacement taxi

Taxiing a floatplane at low speed so the floats sit deep in the water, displacing it like a boat hull. The slowest and most controlled taxi configuration, used in congested areas and near docks.

Float

A pontoon attached to the underside of an airplane to allow water operations. Floats are typically made of aluminum and contain multiple watertight compartments. Also called a pontoon.

Floatplane

A seaplane that uses pontoon floats attached beneath a conventional airframe. The fuselage stays above the water; the floats provide buoyancy and serve as the water-contact surface during takeoff and landing.

Flying boat

A seaplane whose fuselage is shaped like a boat hull and sits directly in the water. Small sponson floats under the wings provide lateral stability. Less common today than floatplanes.

Glassy water

A flat-calm, mirror-like water surface with no wind ripple. Glassy water makes altitude judgment difficult because the pilot cannot see surface texture. Requires a specific power-on approach technique taught in seaplane training.

Idle taxi

Taxiing with the engine at idle power. The floatplane moves slowly through the water, displacing it. Used for maneuvering in tight spaces and near docks.

NOTAM

Notice to air missions (formerly notice to airmen). An official notice issued by aviation authorities containing information about hazards, restrictions, or changes that pilots need to know. NOTAMs may affect seaplane bases — for example, a temporary closure or a water hazard.

Planing

The state in which a floatplane's floats ride on top of the water surface rather than pushing through it. Planing dramatically reduces drag and is necessary to reach takeoff speed. Contrasted with displacement, where the floats sit deep in the water.

Plow taxi

Taxiing with high power and the nose raised, so the floats push through the water at a high angle. Creates a large wake and is used for short bursts to maneuver in wind or to break free from suction on glassy water. Not a normal sustained taxi configuration.

Seaplane

Any airplane designed to take off from and land on water. The umbrella term that includes floatplanes, flying boats, and amphibians.

Seaplane base

A designated area of water used for seaplane operations, including any associated docks, ramps, and facilities. Also called a waterdrome or water aerodrome. Listed seaplane bases have FAA or Transport Canada identifiers and appear on aviation charts.

Step

A sharp break in the bottom surface of a float or flying-boat hull, located roughly two-thirds of the way back. During acceleration, the airplane rises onto the flat section forward of the step, breaking the water's grip on the aft portion and dramatically reducing drag. Getting on the step is a fundamental seaplane skill.

Step taxi

Taxiing on the step at high speed, with the floats planing on the water surface. The airplane is moving fast but not yet at flying speed. Used to cover distance quickly on open water. Requires clear sightlines and awareness of other traffic.

Water aerodrome

The ICAO term for a designated water area, including buildings, installations, and equipment, used for the arrival, departure, and surface movement of aircraft. The formal international equivalent of seaplane base or waterdrome.

Water rudder

A small rudder attached to the back of each float, connected to the airplane's rudder pedals. Provides directional control during water taxi. Retracted before takeoff and landing to prevent damage. Without water rudders, the pilot steers using differential power, air rudder, and wind.

Waterdrome

A designated area of water where seaplanes take off and land. From water + aerodrome. Synonymous with seaplane base and water aerodrome. The term is used internationally and is the namesake of waterdrome.com.