Translation of the verse 6 from Surah At-Takwir : Number of verses 29 - - page 586 - Part 30.
And when the seas shall become as blazing Fire or shall overflow;
And when the seas are filled with flame
(81:6) when the seas shall be set boiling, *6
*6) The word sujjirat as used in the original in passive voice from tasjir in the past tense. Tasjir means to kindle fire in the oven. Apparently it seems strange that on the Resurrection Day fire would blaze up in the oceans. But if the truth about water is kept in view, nothing would seem strange. It is a miracle of God that He combined oxygen and hydrogen, one of which helps kindle the fire and the other gets kindled of itself and by the combination of both He created a substance like water which is used to put out fire. A simple manifestation of Allah's power is enough to change this composition of water so that the two gases are separated and begin to burn and help cause a blaze, which is their basic characteristic.
Source : At-Takwir Verse 6: And when the seas are filled with flame