| metre sea water | |
|---|---|
 Hyperbaric chamber pressure gauge calibrated in msw and bar | |
| General information | |
| Unit of | pressure |
| Symbol | msw |
| Conversions | |
| 1 msw in ... | ... is equal to ... |
| SI units | = 10000.0 Pa |
| CGS units | = 100000 Ba |
| U.S. customary | ≈ 3.263 fsw ≈ 1.45038 psi |
| foot sea water | |
|---|---|
 Pressure gauge on Siebe Gorman manual diver's pump calibrated in fsw and psi | |
| General information | |
| Unit of | pressure |
| Symbol | fsw |
| Conversions | |
| 1 fsw in ... | ... is equal to ... |
| SI units | ≈ 3064.3 Pa |
| CGS units | ≈ 30643 Ba |
| U.S. customary | ≈ 0.44444 psi |
The metre (or meter) sea water (msw) is a metric unit of pressure used in underwater diving. It is defined as one tenth of a bar.[1][2]
The unit used in the US is the foot sea water (fsw), based on standard gravity and a sea-water density of 64 lb/ft3. According to the US Navy Diving Manual, one fsw equals 0.30643 msw, 0.030643 bar, or 0.44444 psi,[1][2] though elsewhere it states that 33 fsw is 14.7 psi (one atmosphere), which gives one fsw equal to about 0.445 psi.[3]
The msw and fsw are the conventional units for measurement of diver pressure exposure used in decompression tables and the unit of calibration for pneumofathometers and hyperbaric chamber pressure gauges.[4]