Basic treatments can be had for cash. Most countries operate a decent medical
system but it's based on cash in advance. Locals without cash usually are left to alternative treatments. They don't do as well. Boating
accidents are not uncommon so the host of broken bones and nasty cuts and other assorted trauma injuries are something no one is immune from.
If you need specialized treatments you'll most always need to travel to another location. You'll more likely need a policy that can pay you back since service
is mostly cash in advance until you get to the most civilized locations. It won't cover travel unless you get a specific evacuation policy. If you are in the same hemisphere those policies can be had at a reasonable cost. Even if all you have is a way to bail out and a place to go it could be part of a solution.
Many don't carry any insurance health or otherwise. Friends that left just after 9/11 got back a year ago and have been catching up on delayed health care
for the better part of a year with minor surgeries and extended tests. The revenge for being away cruising 7 years often causes the disease that has no cure - age. You can lead an active and healthy lifestyle and still get older and have problems to deal with. These are people that were never sick and just suffered the serious problem of turning 50. We usually have a few stories each year where the husband has a heart attack and ends it in a short span of time. Being away does not accrue extra health.
has to exist in a spectrum of solutions. From the first aid kit all the way up to an emergency
evacuation. I don't think you can really assemble a single
policy to cover that. Some things beyond just the most basic you need to be able to treat ASAP and then seek extra help. Your first aid skills should be expanded to include more than you do now. You can go through several of the Red Cross courses locally. There is a lot of information here already on those topics of how to prepare for more first aid training.
A good understanding of your current
health is clearly something required. Finding a way to get an annual physical isn't such a bad thing either. You can be proactive and should be when out away from most of the world.