Final answer:
The Alvin is the correct answer as it is a manned submersible, unlike ROVs and AUVs which are unmanned. It has adjustable density for deep-sea exploration.
Step-by-step explanation:
An example of a manned submersible would be the Alvin. The Alvin is a well-known submersible that has been used for deep-sea exploration and is capable of carrying a crew, which distinguishes it from unmanned vehicles like ROVs (Remote Operated Vehicles) and AUVs (Autonomous Underwater Vehicles).
Submersibles like the Alvin have adjustable density, including ballast tanks, allowing them to float or sink according to the crew's requirements, similar to submarines described in the figures provided.