It's going to vary depending on circumstances. If you are engaging in an activity where this is a realistic possibility, there should be a discussion about it. I recently sailed a boat from Los Angeles to Hawaii, and while the trip isn't especially dangerous you are far from emergency medical care. One of the guys did tell me that he would want to be buried at sea. The alternatives are not great if you are far from shore, how long does unrefrigerated meat last in the tropics? Some hikes and climbs it might be realistic to bring the person back, other times you might need to plan a return trip.