Margaret St Clair 
Dolphins of Altair [EPUB ebook] 

Before the dawn of man . . .. . . there was a covenant between the land and the sea people — a covenant long forgotten by those who stayed on shore, but indelibly etched in the minds of others — the dolphins of Altair.Now the covenant had been broken. Dolphins were being wantonly sacrificed in the name of scientific research, their waters increasingly polluted, their number dangerously diminished. They had to find allies and strike back. Allies willing to sever their own earthly bonds for the sake of their sea brothers — willing, if necessary, to execute the destruction of the whole human race . . .