The United Kingdom's Royal Naval Air Service, keen on developing the new medium of aerial warfare, converted a number of vessels as seaplane tenders for scouting purposes.
Similarly, battleships began to mount short flight decks on top of gun turrets, enabling small single seat aircraft to take-off from them.
During World War I, other more satisfactory (although still clumsy) solutions had been found, in which turret platforms, and later (when aircraft got heavier) catapults were mounted on battleships, cruisers and seaplane tenders, used to launch scout planes.
During World War II, observation-scouts were essential for battleships and other surface warships during bombardment of land targets.
Due to the improved technology used by today's naval vessels, and the use of ship-launched UAVs for the same sorts of "spotting" missions in the 21st century, scouts are no longer needed for long range exchanges.