Bihaar (plural) for sea … i.e All the seas
Sujirat – Tasjeer; to be filled , to be ignited (with fire), or dry out.
Hence Ibn Kathir translated this verse as, ‘And when the seas become as blazing fire’
Based upon this some Ulamaa said the seas will over flow others said it will be ignited and others said it will dry out and some Ulamaa said all of the above will happen but at different times
Imagine for a second if All the water in all the oceans was fuel for a fire, imagine the intensity and ferociousness of such a fire.