As a new owner, you should run with another boat for a while for sure. Chances are high for a screw up early on. If you don't have one, get an automatic inflating life jacket, maintain it and wear it, particularly when alone and/or running in and out of deep water.
Obviously you can't carry everything, but here is my list of key items in my boat not covered already:
- First aid kit, goes without saying.
- Spare fuel filter, spark plugs and other basics.
- 5 gallon bucket, normally used for garbage, but can be used to bail the boat, throwing water on a fire etc.
- Mosquito net hammock and tarp (this is my standard camping kit anyway).
- Lithium battery jump box, double bagged in zip locks. I found one that will start my AV motor with no other battery. It will also charge phones etc.
- Keep your cell phone in waterproof case or bag, otherwise it is useless if you sink.
- This does not apply to all, but I carry a spare set of glasses, otherwise I am stumbling around blind.
One more item that I added this past year is a Garmin InReach Explorer GPS/Satellite communicator which provides 2 way text and e-mail on the Iridium network. It can be used to send your position to recipients with messages and contact authorities if needed. Being Satellite connected, it works where cell does not. They cost about $500 to purchase and get connected. The cheapest subscription plan is only $15 per month that covers 10 texts per month, but additional texts are 50 cents each, pretty cheap if you really need it. You can change the plan monthly as needed with $65 covering unlimited messaging, which is cheaper than international cell plans. The unit is waterproof and can be used most anywhere in the world. Use it for offshore fishing, trips to the islands and international travel too.
I previously tried a SPOT tracker/communicator, but it was a 1 way only device, the unit can send pre-selected messages only and can't receive messages. It requires too much pre-trip coordination with your buddies and you get no indication that messages were received.