The low velocity sound region in the ocean is controlled by what two properties of water?

Temperature and Pressure

Explanation:

The velocity of sound in water decreases with decrease in temperature with increasing depth of ocean.

Also the velocity of sound in water increases with increasing pressure due to depth of ocean.

After a certain depth (nearly 2460 feet) the decrease in temperature becomes negligible and hence change in velocity of sound due to change in temperature with depth becomes negligible too.

This region of ocean is used as low velocity sound channel or SOFAR (SOund Fixing And Ranging) channel.