Generally, with a few exceptions, the preflight inspection of a seaplane is similar to that of a landplane. The major difference is the checking of floats or hull. The manufacturer's manual or handbook should be used in conducting the inspection.
The pilot should first note how the seaplane is setting in the water prior to each flight. If the sterns of the floats are very low in the water, consideration should be given to how the seaplane is loaded. Also, if lower than normal for a given load, a rear compartment may have a leak.
Floats and hulls should be inspected for obvious or apparent defects and damage, such as loose rivets, corrosion, separation of seams, punctures, and general condition of the metal skin. Because of the rigidity of the float installation, fittings and adjacent structure should be checked for cracks, defective welds, proper attachment, alignment, and safetying. All hinged points should be examined for wear and corrosion, particularly if the seaplane is operated in salt water. If water rudders are installed, they should be inspected for free and proper movement.
It is important to check each compartment of the floats or hull for any accumulation of water before flight. Even a small amount of water, such as a cup full, is not unusual and can occur from condensation or normal leakage. All water should be removed before flight, because the water may critically affect the location of the seaplane's center of gravity.
If an excessive amount of water is found, a thorough search for the leak should be made. If drain plugs and inspection plates are installed, a systematic method of removing and reinstalling these plugs and plates securely should be used. Naturally, it is extremely important to ensure that all drain plugs and inspection plates are securely in place before launching the seaplane onto the water. It is recommended that each plug and plate be counted and placed in a receptacle upon removal and counted again when reinstalled.
Float compartments, water rudders, etc., should be inspected for ice if near freezing temperatures are encountered. Airframe icing, resulting from water spray during a takeoff or landing, must also be considered. Part of the preflight inspection should include a cabin inspection. All items must be secured, such as anchors and paddles prior to takeoff. Flotation gear should be available for each occupant.
During the preflight and boarding of passengers, a thorough passenger briefing is very important. Evacuation of a seaplane causes a few problems not encountered with the landplane. Location and operation of regular and emergency exits should be known by all persons on board. The pilot should assure that all passengers are familiar with operation of seatbelts and shoulder harnesses, most especially that all persons can UNFASTEN their own seatbelts and shoulder harnesses in the event an accident occurs on the water.
Before beginning any seaplane operation, it is especially advisable to consider the existing and expected water condition, and the windspeed and direction to determine their combined effects on the operation.