1957 Satellites- These gathered information mainly about the ocean surface over large areas. These helped quite a bit because they took pictures, depths and just a better understanding of the ocean, river, lake, etc.
1906 Bouys- These are floating objects that helped study the hydrosphere because it measured both the characteristics of the water and the currents at a particular location, so this did two things at once! It also aids to navigation because they are anchored in the water and mark the channel limit and channel junctions, identify boating hazards, or provide other information.
Early 1500's Submarine (Submersiles)- These allowed people to explore deep sea levels and exploring the underwater. It also allowed people to discover marine life that could not be discovered by other technologies created then. They were not only used for exploring the sea levels but also used in war or for delivering weapons.
