submersible
n.a small boat or vehicle that can travel underwater. It is usually used for research or to explore the deep ocean.
n.a small, self-propelled vehicle capable of operating underwater. Often used for deep-sea exploration or scientific research.
“The scientists used a submersible to study the ocean floor.”
“The research team spent three days inside the submersible, collecting samples from the deep-sea vents.”
“While large submarines are designed for military or long-range transport, a submersible is typically a smaller, more maneuverable craft intended for specialized underwater observation and data collection.”
“David Bushnell developed the "Turtle" submersible as a student at Yale University.”
From submerse + -ible.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.