Question 65489
First: there is too much of it (60-70% of the earth's surface is wet).
Second: it is very deep in many places (miles deep) & it takes very special & expensive equipment, along with brave men/women to go to the bottom.
Third, the ocean floor is ever changing. There are thermal cracks across most of the major oceans.
Fourth: we are spending almost all our exploration dollars in our space program to the deterement of the ocean investigation. We, someday may need to not only explore the bottom of the oceans, but may have to live there if we mess up our atmosphere with nuclear or natural contaminants which make living on the land impossible.
Hope this gives you some ideas but I don't have too many scientific knowledge on this subject.
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MERRY CHRISTMAS.