pumping with water

Hello there.

So, I was just thinking the other day while pumping, if there is any difference in pressure with water inside the cylinder. (we are talking about air pumping devices)
Example:
You have large cylinder, large enough that you can get inside your whole erect penis and enough hot water to keep your penis fully sunk under water. And you will still have enough room for air in your cylinder so no water will get sucked into hose and pumping pistol.
Will there be a difference in pressure on your penis because of that water? (of course you pump to the same pressure level with and without water…)

The reason why I am asking is because:
1) I do not know the answer and I am curious
2) I tried it and with water I do not feel the same pressure like I do without the water. That is why this question came up to my mind.

I’ve done that in the bath.

Just have to leave enough air to pump out.

Yes there is a slight difference in pressures due to the weight of the water. Weight of water is positive pressure which would reduce the amount of vacuum (negative pressure) the dick is exposed to.

A simplistic example is:
Assumptions:
8” tube pointed straight up with 6” water, a 5.5” dick and -5inHg vacuum in the air gap of the tube

Data:
Total vaccum is: 0 psia = -30 inHg = -14.7 psig
so
-5inHg = -2.45psig

Weight of fresh water = 8.33 lbs/gal = 0.052 psi/ft

Calculating the vacuum pressure at the base of the tube (bottom of 6” water column):

Pvac@base = Pvac@surface + weight of 6” water column
Pvac@base = -2.45psig + 0.5ft*0.052 psi/ft
Pvac@base = -2.45psig + 0.026psi
Pvac@base = -2.424psig
or
Pvac@base = -4.94 inHg

Thank you, sir!