They cover large distances.
They can go on long-term missions.
They're autonomous, unmanned systems, so you don't need a large number of people on board.
They can include many different sensors to measure many kinds of data such as temperature, salinity
They allow us to collect almost real-time data.
The glider would be not heavy.
The glider is easy to fly.
The glider easy to make and formed because it use of material easy to be obtained in any place.
To make glider not require cost many / high. Suitable to all age including children.
gliders carry ballast tanks filled with water. Heavier gliders sink faster than lighter gliders.