Some talk about Deckvests....another data point:
I was at a Safety At Sea Class in last February in Wisconsin. A number of sailors there are Chicago Mac sailors. My Deckvest Hammar Hydrostatic did not inflate when I jumped in to the pool. A few other Deckvests did not inflate either. The response from the Deckvest rep said I needed to be lower in the water for it to go off. They are designed for a maintenance guy falling off an oil rig with a tool belt. when they are below the water they will activate. The issue is...with my foulies and boots, I was bouyant and did not drop below the waterline. This, to me, is a major design flaw or rather wrong application of technology to the situation of a sailor in the water. All the aspirin tab type auto inflators worked, including my 12 year old vintage PFD/Harness.
I highly suggest the Safety at Sea course and jumping in with your typical gear. Do you float or not? You will be suprised. I was surprised how bouyant my Dubarry Offshore boots were. I'm keeping them on.