I don't know. Both seem potentially traumatic, but it would depend on the scenario. If the fire killed me by smoke inhalation or CO poisoning (as most fire deaths occur that way), then that would be a little easier. In fact, in the past I have considered dying by inhaling car exhaust until I go unconscious. On the other hand physically burning to death would be entirely too slow and painful to even consider.
Likewise, a tsunami could slam me into a brick wall and kill me instantly, which wouldn't be as bad, but it could also pin me under debris where I would slowly drown over 5 or 6 agonizing minutes. It would totally depend on the scenario in either case. But suffice it to say that slow and agonizing is not on my "to do" list in any case.
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~Nick
Misunderstood since 1979