rlboyce wrote:I am no diver so I am unaware of the importance of such matters, but would it make a difference if there was a high water flow, or if the water was flowing in/out?
Water flow affects visibility, depending on the cave. High flow can either wash-in debris and ruin the visibility, or wash-out the debris and improve visibility.
Flow also affects how much gas you utilize, or conversely, how much gas you have to bring with you, and limits how far you can penetrate into the cave.
In a spring, the water flow is out
of the cave. Therefore you have to fight against the current to penetrate into the cave. If the flow is high, you've got to work rather hard. Therefore you burn through your gas much faster, and your penetration distance is limited. You get a free ride heading out of the cave, though.
In a siphon, the water flow is into
the cave. I don't dive siphons anymore, don't care for them. In a siphon you are carried with the current as you enter the cave, but then you have to fight against the current to exit the cave. If you plan properly you have enough gas to make it out alive!
For example, in one cave with no flow I was able to penetrate over 3,500 feet with a single set of tanks before we had to turn around. In another cave with high flow (a spring), I was able to penentrate only 800 feet before my gas supplies required that we turned around. Big difference.