batho-, bathy- +

1. Any earthquake that happens at great depth.
2. An earthquake of deep origin recordable at seismographic stations around the world.

Pertaining to the depths of the ocean.

A reference to a knowledge of deep-sea life and conditions.

A spherical deep-diving chamber in which people are lowered by a cable from a surface vessel to study the oceans and deep-sea life.
2. A tethered metal sphere with an inside diameter of less than three feet in which the deep-sea pioneers cramp themselves for several hours during each immersion.

In 1934, a bathysphere carrying William Beebe and an associate reached a record depth of over 923 meters (3,028 feet).

Because space in the bathysphere is cramped, dives longer than three-and-a-half hours are intolerable, and it was eventually replaced by the bathyscaphe.

The record that is made by a bathythermograph (an instrument that records water temperature in relation to ocean depth).

1. A device for obtaining a record of temperature against depth (pressure) in the ocean from a ship that is underway or in motion.
2. An instrument for recording water temperature as compared to depth.

A ship; such as, a bathysphere or submarine, designed to operate far below the surface of the water.

1. A line connecting the points on the surface of the earth where a certain temperature is found at the same depth.
2. A line or surface showing the depths in oceans or lakes at which points have the same temperature.

Isobathytherms are usually drawn to show cross sections of the water mass.