Bermude Triangle

Two thing -- first, the drop in "coverage" over unexplained phenomena in the triangle are probably the result of better science, hence less unexplained losses as well as better communication between ships and shore, so people actually know why boats and planes are lost. The boats and planes are now also equipped with non-magnetic navigation devices, such as GPS, so navigation has become much better.

Another phenomena that might help explain losses is "rogue" waves -- giant ocean waves that were previously thought not to exist. These waves can be upwards of 100+ feet in height and take a large vessel by surprise. Although these vessels might be able to handle such waves when they're ready for them, these waves can "sneak" up on a large ship and hit it abeam and break it or sink it altogether.

Weather, Methane, and giant waves might explain some things, but it doesn't explain everything.

missing ship and airplane lists

plane crash

electromagnetic anomalies

the unexplained

the triangle on the Grid

I think there's rumoured to be one around LA in the US too, although having said that google isn't coming up with anything.

Navigational charts show a magnetic anomaly out to sea a ways off L.A.

Aircraft sectionals show another magnetic anomaly in the mountains of Nevada north and a little ways west of Reno.
(It could be in California in the same general area, just across the border from Nevada - from memory, so I'm not 100% sure on the exact location, but it does exist.)

Magnetic anomalies are present in many areas of the world.
I believe most of them have been located and show up on charts, sectionals and maps.