What is thought to be the primary function of the vibrissae on a seal or sea lion?

Many mammals (unfortunately not including humans) have specially adapted hairs on their faces, called vibrissae, that are used as tactile sensory organs. They can be precisely manipulated to move forward or backward, and they will send a neurological response at the slightest touch.

The vibrissal plume of seals and sea lions is an extra cut above that of most other mammals, their whiskers can sense the most minute changes in the movement of water to detect prey in conditions of low visibility, and can even be used as an early warning system to avoid collisions with rocks and other seals due to how fast the response reaches their brains.