A big survival knife and a firearm (preferably a serious caliber rifle) would be great in a survival situation on land, but we were discussing aviation survival -- at least I was. First you need to egress the aircraft intact and predominantly uninjured before you are allowed to do battle with the beasts.

My survival priority was: 1) Egress, 2) Flotation, 3) Signaling.

For egress the idea was to minimize the bulk of what I carried to make swimming and getting outside the aircraft expediently. Flotation is fairly straightforward, but for that I went to Switlik which must be considered one of the leaders in the field. I went heavy on signaling, with lights, mirrors, flares, a VHF Marine radio and a PLB. No, you can't rely on the pilot to carry one. The aircraft may have an ELT but it may sink with the aircraft. So I carried my own.

A big knife and gun are great if you're on your own, but a PLB will get you out of the situation and it's a heck of a lot smaller and lighter than two big pieces of steel.

$.02, YMMV