It is my understanding that yachts, like Embassy's, are considered territorial extensions of their country of origin, which is why Coast Guards (US and otherwise) need prior agreements with other countries to go aboard ships (and yachts) of such countries on the open ocean absent hostilities--and why a USCG may board a US vessell anywhere in the world. If one has a crew that passes away--of natural causes or otherwise-on the open sea, the venue of jurisdiction is the country of origin of the yacht. If the death occurs within the territorial waters of another country, that country is the venue of jurisdiction. If one suffered the loss of a crew at sea and had no way to preserve the body for interment ashore, one would, of course, have no choice but to bury the body at sea although that involves somewhat more than simply tossing the body overboard (at least if done properly) and must be thoroughly and completely logged or otherwise documented. It is not a pleasent subject to consider but one that should be discussed at some point in passage planning, particularly among couples.
"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."