Re: Send packing the stuffing gland..
The PSS seal is based on a graphite-to-stainless contact. The graphite is in the form of a "donut" that is attached to a polymer bellows that is compressed about 3/4". The bellows acts like a spring to keep the graphite "donut" pressed against a highly polished stainless steel rotor. The rotor is a tight fit to the shaft and includes 2 o-rings to assure no water leaks past the rotor where it contacts the shaft.
Graphite is an inherent "lubricant", so I'm not sure what the water does--other than perhaps providing cooling to keep the rotor from getting hot. The design of the seal is such that the graphite-stainless interface is dry and does not normally see water. If that were the case, the "dripless" shaft seal would drip.
Final note: I replaced by bellows and o-rings, but the graphite stator and the SS rotor are entering their 23rd year of service, with no end in sight. I would not worry about water circulation to the seal on a sailboat.