I suggest second opinion just to be sure it's rotting. A towering water oak was removed last year further up on Coral Way when arborist recommended doing so because of "rot".... a day and literally hundreds of dollars later the home owner was shocked to discover that there wasn't any rot but it was too late. Friendly advice only.... the oaks make the beautiful neighborhood what it is and just can't be replaced one for one with skinny palms for the same shade and beautification benefits.