Do seaplanes need to get clearance for takeoff? Do seaplanes need to get clearance for takeoff? Do they have ATC? How do seaplanes get clearance to takeoff?
If the seaplane is operating from a land airport with a control tower AND a water runway, yes.  Or, if the seaplane is operating from a Tower controlled  water-only aerodrome, such as the one along the waterfront in Vancouver BC in Canada, yes also.  Same radio procedures as any other airplane.  

Otherwise, no.