I just have two large waterproof flare containers under the front seat one of which has all the "safety" and other kit in it. Don't really see the point of carrying another bag with even more kit.
Some of the stuff quoted doesn't seem very useful in coastal waters IMO, that is we are unlikely to be marooned on a desert island for a long time.
We carry on our lifejackets or in the pockets of the flotation suit a GPS EPIRB, waterproof VHF, spray hoods and lights. Apart from a knife I can think of much else except maybe a personal flare that would be of much utility.
There are plenty of emergency flares and safety items (including a lighter
) in the safety box mentioned.
My intention would be to stay with the boat, if I have left then it is either we have been thrown out by hitting something or the boat is on fire. In either case it seems unlikely we would have time to collect anything even from under a seat.
In an emergency we would use the kit on the boat, if in the sea with little warning the priority is staying warm and calling for help, both of which are taken care of by the kit carried on our persons