male stinger 36 is removed the bellows 60 expands to engage the upper poppet head 51 the bias force stored energy in the contracted bellows 60 pushes the poppet head 51 upward back to the closed position of fig2 sea water applies hydrostatic pressure in the space 66 and to the bellows 60 outer surface the pressure inside the bellows 60 may be less than hydrostatic however the hydrostatic pressure alone cannot open the coupler 34 as shown in fig3 referring now to fig4 a schematic example is presented for an explanation of why forming the bellows 60 diameter where it connects to the lower base 58 to be less than the upper poppet head 51 diameter self seals the coupler 34 as is known the force from pressurizing a surface is a function of total surface area thus the pressure seal between the upper poppet head 51 and upper base 56 will be maintained if the resultant force of ambient pressure applied to the base 56 and bellows 60 a has an upwardly directed vector referring back to fig2 and 3 and assuming the bellows 60 follows a repeating path resulting forces taken along a period 90 degrees 180 degrees 360.