English Translation
The disappearances in the Bermuda Triangle are inexplicable.
失踪 in this context sounds unnatural a bit. 失踪する is usually used when a person INTENTIONALLY disappeared whereas 行方不明になる can include both intentional and unintentional (e.g. kidnapped or technical accident) missing cases.
Also, the Japanese sentence is more likely to refer to a single MIA case. But the Bermuda Triangle is a famous section where many ships and airplanes disappeared. My alternative translation is:
バミューダ・トライアングルでの消息不明多発は不可解だ。（しょうそくふめいたはつはふかかいだ）
We usually spell Bermuda as バミューダ, but バーミューダ is also (not common but) okay.