If your propshaft seal is a Volvo, it's a triple lip oil seal design with no moving parts - very smart and simple, with a water pick up and discharge below the WL. To burble you squeeze/deform the lips.
Volvo also recommends annual lubrication with lubriplate AA-130 white lithium grease and replacement every 5 years. I bought a spare seal from Syselios, it came with a bit of grease. Later bought some "OEM" grease separately for $10+, it was also only a bit. So next time I will be looking for a large cartridge from a generic source.
You shove the grease under the lips while deforming/squeezing hopefully on the hard. Presume this would be more of a challenge in the water.
2005 B473 Lake Ontario
Light travels faster than sound. That's why some people appear bright until you hear them speak.