The real mystery of the Bermuda Triangle is the result of not knowing why a ship or a plane suddenly loses contact, and never to be heard from again. However this mystery "is" based on fact, a fact that ships and planes have in the distant past, as well as in the last few years, disappear in this area of the ocean for no known reason.
There are several experiments that were and are carried out in the hopes of solving the mystery of their disappearance, but so far they have only come very close, but not completely support their theory of what actually causes these events.
In two experiments involving methane gas as one possibility, it was found that huge volumes of methane that rises from the ocean floor from time to time could in fact sink a ship as the methane displaces the ability or buoyncy of water to support the weight of a ship or smaller boat. This experiment was carried out after one large offshore oil rig lost buoyancy following a large amount of methane bubbling from the ocean floor right next to the rig.
The other theory that methane could be responsible for planes suddenly exploding as a result of flying through methane gases, was thought to be because of a spark or the hot exhaust of the plane igniting the gas causing an explosion.
As experiments go, they do not always provide an answer because the exact conditions must be met in order for them to work. Those who feel that there are mysterious forces at work are only focusing on things that are not easily understood, and therefore becomes the mystery.
Gravity if given any thought, can be considered a real mystery because it is a force that cannot be seen, but felt. There are unknown forces on this planet, and throughout the Universe, that we still do not have answers for, but they are present, and until we can get a handle on how these forces work, it remains a mystery.
Some seem to think the simple explanation for these events in the triangle are a result of the elements at work, and dispel any notion that there were forces beyond our understanding that cause these events.
Well, in some cases maybe so, but that does not provide an answer for the sudden disappearance of a plane or a ship where there was no weather conditions that would cause such a disappearance.
Many of these events happened with mild weather conditions as well as normal communications when suddenly there is no further response moments after all seemed normal. So what would cause these sudden disasters is the mystery, and that mystery is based on the "fact" that these ships and planes disappear for no known reason.
That being the case, the mystery of the triangle is really based on factual events that present a mystery.