Who would want to pack up, move, renounce citizenship and all this just so one could pay no tax on trading? Sounds to me like you would have to be a very serious chap to sacrifice modern technologies, health care providers and safety just to save a little on trading. Must have a bundle to trade it that is the case.
If you are on that boat, and you find a way to pay no taxes, and your boat gets into trouble out on the water, who would feel would have the obligation to rescue you? Pay no taxes, receive no services.
No problem: (1) If you want to live on a boat, you have to do it in style. Many of the 'richer' people in the world live on boats. Such boats cost from $20Million up. Some Italian builders from around Genua know how to make real nice and cozy ones. The crew depends on the degree of automation: goes from 4 to 20. (2) No danger on the sea. The thing is run by professionals. These people navigate mostly from one port to the other in the Mediterranean which is kind of a safe well 'kept' little sea: no pirates like on other seas of the world on the lookout for non-tax paying individuals. Technology on board helps you to get into a safe port ahead of bad weather. (3) You should watch that you don't berth up too long in a port or the local tax people will try to make you a 'resident'. (4) You don't pay taxes but you 'pay as you go': salaries, port costs & bribes. No pipe-dream but reality for the few. If your budget doesn't make you fit into this category, I agree that 'living on a boat to avoid taxes' could imply a rather harsh lifestyle.
Where i live payments in cash are forbidden above a certain amount. I don't know the exact amount, but buying a car with cash is impossible. All cash transfers above 10 000 $ have to be reported by the bank to a fiscal cell and will be analyzed. It's just a matter of time before this will be the general rule all over the world.
Belgium. If you want to deposit money in cash on someone else bankaccount you need a power of attorney to do so or your deposit will be refused.