Revelation 8:8

Then the second angel sounded:  and something like a great mountain burning with fire was thrown into the sea, and a third of the sea became blood.

·         Something like a great mountain: John carefully says that this is not an actual mountain (note the use of like), but it is a blazing mass as large as a mountain. (DG)

·         The sea may be a specific reference to the Mediterranean and not a reference to all oceans. For a person in the world John lived in, the Mediterranean Sea was the sea, and they really had little knowledge of other oceans. (DG)