Which term refers to an underwater vehicle specially constructed for ocean exploration?

The term that refers to an underwater vehicle specially constructed for ocean exploration is "submersible." Submersibles are designed to operate underwater and are equipped for scientific research, exploration, or to gather data from the ocean depths. Unlike submarines, which can operate independently, submersibles usually require a support vessel and have limited operational time underwater due to power constraints and capacity limitations.

The other terms listed do not describe underwater vehicles. A tidal bore refers to a phenomenon where a tidal wave travels upstream in a river. A tidal datum is a reference point used for measuring the elevation of the sea level, which assists in understanding tide patterns but is unrelated to actual underwater exploration. An amphidromic point is a theoretical point in the ocean where the tide has zero amplitude, which is a concept in tidal theory and is also not related to underwater vehicles.