You have failed to mention exactly how long ago this dream was, but I think that it sounds very like the predictions which many of the scientists are now making about a great proportion of the eastern seaboard of the United States being well under water as a result of the melting polar ice caps and rising sea levels caused by global warming.
Some of the smaller Pacific island countries are already looking down the barrel when it comes to the ocean rapidly encroaching on the solid land on which they are living, so perhaps you could be seeing in your dream one possible future if we are because of ignorance, fighting between ourselves, a lack of international co-operation and excessive government red tape unable to turn these potentially catastrophic climatic changes around in time to save the planet and our own lifestyles as we once knew them.
But this does not mean that there is only one possible future outcome.
We can by working together I believe still greatly reduce the probability of this happening as seriously as you saw in your dream, although I no longer feel that such major climatic changes can be avoided entirely.
We will need to plan around this happening to some extent over the next 40 or so years (by 2050), but to what degree is still to be seen.
Knowing that your own family is OK is surely cold comfort for those who have lost everything and everyone who is important to them to the rising waters and possibly more devastating tsunamis.
If we can only work together with both wisdom and tolerance for both ourselves and those in other countries, then I believe that we still have a reasonable chance to prepare for what may to some extent lie ahead for us in the future with regards to major climatic change, but nobody should think for a moment that the situation is entirely stoppable or reversible.
Dreams which involve especially vivid imagery and remain in our memories (as if permanently imprinted on our retinas) effectively for the rest of our lives are believed to come more directly and often from our unconscious mind's spiritual centre (our Higher Self), or be an subconscious expression of a shared hope or fear of the entire human species as a whole.
EoT
