Peggy, I'm writing you because you seem to have a lot of experience in boat odors and other stange discharges form the bowels of boats. I have a 1996 Hunter 37.5 and recently I have noticed a strange black substance in the bilge water. It does not appear to be oil but it is heavier than water. I does have an unpleasant smell however. I mentioned my boat because on this model the engine bilge does not drain into the main bilge so oil from the engine can not enter the main bilge. The only drainage into the main bilge is from the refrigerator, the cutlass drip and maybe the air conditioners condensation. It is staining the bigle black. Can't figure out what it is, any ideas? By the way, read your book twice, very helpful and should be included with every new boat purchase.