Diving 107: Scuba Diving Underwater Physics

• 33.03 feet sea water = 1 Atmosphere pressure = 14.7 psi
• 34.03 feet fresh water = 1 Atmosphere pressure = 14.7 psi
• PV=nRT
• P=T/V or V=T/P or T=PV
  • P = pressure in psi
  • V = volume in ft3
  • n = moles of gas (1 mole = 6.022 x 1023 atoms)
  • R = gas constant 10.7316 psi ft3 / lbmol °R
  • T = temperature in Rankine (°R) = °F + 459.6
• Pguage = 14.7psi x [depth of sea water] / 33.03 feet sea water
• Pabsolute = 14.7 + (14.7psi x [depth of sea water] / 33.03 feet sea water)
• Sea water weighs 64.58 lbs/ft3 pr 8.6213 lbs/gallon Specific gravity = 1.035
• Fresh water weighs 62.4 lbs/ft3 or 8.3303 lbs/gallon Specific gravity = 1.000
• Bouyant Force (Archemedes Principle): Fbuoyant = Win air - Win water = dgv
  • Fbuoyant is the buoyant force
  • Win air also known as dry weight
  • Win water is weight in water [remember that negative numbers are positively buoyant]
  • d is the density of the liquid [salt water is 64.58 lbs/ft3 and fresh water is 62.4 lbs/ft3]
  • g is the gravitational acceleration 32.37 ft/sec2 (normally written as 1 in the equation i.e. 1 gravity)
  • v is the volume of the object in cubic feet (ft3)
• For calculating the tissue depth for Haldanean decompression M-values, an easy to remember formula is:
  • Dfinal = the final tissue depth
  • Dactual = actual dive depth
  • t = time underwater
  • h = halftime compartment
• I have written a function for the R language which calculates the EAD, PO2 and working depth for any FO2 breathing gas blend.
  • You can find my simple function here: http://quashnick.net/scuba/university/Nitrox_for_R.txt
  • A better option is to use the http://www.R-Project Package called scuba. You can find it here: http://cran.r-project.org/src/contrib/Descriptions/scuba.html

Other Dive Related Pages

1. California Kelp Diving and the Kelp Crawl
2. Freediving and Underwater Hunting
3. Abalone Diving Basics
4. Scuba Equipment Maintenance and Care
5. Scuba Diving Home Remedies and Concoctions
6. Scuba Diving Underwater Physics

External Links

http://physics.itsbaxter.com/links.html - Good site for more information on the physics of scuba diving.