Meanwhile, at the bottom of the ocean, scientists have uncovered a big rock that mysteriously floats to the surface and then takes off like a rocket.
(scientists; have uncovered; a big rock that mysteriously floats to the surface and then takes off like a rocket; T:Meanwhile; L:at the bottom of the ocean) (a big rock; mysteriously floats; to the surface) (a big rock; takes off; T:then)
scientists a big rock a big rock
have uncovered mysteriously floats takes off
a big rock that mysteriously floats to the surface and then takes off like a rocket T:Meanwhile L:at the bottom of the ocean
to the surface
T:then