People usually get confused if you ask them about the most important things they would take with you in case of a fire, earthquake or other kind of disaster. We live in a pretty safe world, so only a few people would be ready to immediately answer the question stated in the title. Things change a bit when it comes to equipment on board. Every crew member or at least the captain should prepare something called a grab bag, a bug-out bag, BOB, or just a survival kit. It should be waterproof and should be able to float on water. It ought to contain items that will help you survive at sea, in case you have to abandon the vessel.
The content of grab bags should be standardized for different areas or types of use. A maritime survival kit should contain different items than the one for a tornado area, or an area with a high risk of wildfires or earthquakes. The items a grab bag should contain are the following: water, dehydrated food, a first aid kit, whistles or a radio communication device, a positioning beacon and similar items. If you run out of food and water, but are not injured, the most helpful tool will be a fishing hook. If you manage to catch a fish, you will satisfy both your thirst and hunger. I suggest you study the fish in the area you are about to sail, even if you are not interested in fishing at all. Some fish could be poisonous, which is an additional problem you do not want to deal with.There are some standardized grab bags at the market, and they can be found under the names such as 72-hour kit, PERK (Personal Emergency Relocation Kit), GOOD bag (Get Out Of Dodge) and INCHbag (I’m Never Coming Home). These kits are made to keep you alive for at least 72 hours because it is believed that 3 days is enough for the rescuers to find you. This estimation, however, cannot be applied to accidents at sea because it is impossible to predict how far from the land an accident might happen.
I wish you a calm sea, a fine wind and a strong mast!Finally, I recommend you always keep a mirror with yourself. I learned this some time ago when I took part in an exercise about team building and leadership in business. The participants had to choose seven items out of twelve offered that they would put into their survival kit. This test apparently originates from the U.S. Navy. One of the items offered was the mirror. Out of five participants in my group, only one chose this particular item. She was a woman, so other members of the group teased her for wanting to look good even in a dangerous situation. That is why we were all surprised when it turned out that the mirror was a thing we should take with ourselves. The woman proudly explained that the mirror is pretty useful if you want to send out a strong light signal. In that respect, the mirror is sometimes worth more than a radio transmitter (which usually does not work).