Dexter Russels work wonders and if lost overboard no big deal they are cheap and easily replaceable
+1 On the Dexter Russell - not fancy but for the price they have a decent edge and even I can get then sharp again so thats saying alot:) I've cut up a boatload of salmon with mine and they have been great.
Don't have one but seems the Bubba Blade fillet knives are supposed to be a pretty good knife.
