The process known as “upwelling” is caused by the winds blowing across the surface of the ocean and push water away. Colder water then rises up from deeper beneath the surface to take the place of the water that was pushed away. It is also the opposite of downwelling.
MSW or Metre Sea Water is the unit used in metric to measure the pressure divers are exposed to. For every meter of sea water the pressure is theoretically 0.1bar and is equal to 3.26336 fsw.