The Sensor Buoy is a Turret in Star Wars: Galactic Battlegrounds: Clone Campaigns that is available in Tech Level 1. It costs 20 Carbon and 10 Ore, and is an aquatic version of the Sentry Post. Like its land-based counterpart, it has an excellent Line of Sight, and can detect stealth units, but cannot attack.
Sensor Buoys are built by Utility Trawlers, and can only be built on water. They can spot an enemy navy from far away, and can be useful when fighting Gungans, as they can detect the Gungans' submerged Frigates.
"A fixed water-based observation structure that provides advanced warning of nearby enemy activity. Sentry Buoys are excellent for detecting stealth units, like Jedi or submerged sea units. Sentry Buoys do not have an attack and are built by a Utility Trawler."
The Sensor Buoy is the only building in the game that has the same icon or appearance for all civilizations.