Peter Locke 
Mikkee the Martian [EPUB ebook] 

Billy and Jilly Watson ask Mikkee the Martian to explain the Bermuda Triangle.

Mikkee replies that it started when an alien spaceship crashed on Earth millions of years ago.

Signals between the Aliens and their home planet cause interruptions in the sea and air in the surrounding area, and ships and planes caught in the disturbance, are trapped in a time bubble,

Mikkee takes the twins to visit one such bubble, where their ship is raided by pirates and they are taken captive,

The trio are made to dig for hidden treasure and then made to walk the plank.

Of course, they all arrive home safely and Jilly persuades Neptune God of the Sea, to release all those trapped in the time bubbles.