After conducting research, I could not find any information on a boat ramp named Cool Branch Road in Quitman County, Georgia. It is possible that the name may have been changed or it may not be a designated public boat ramp. Therefore, I am unable to provide information on its dimensions, the body of water it services, or the types of watercraft permitted.

However, Quitman County does have several public boat ramps available for use, including the George T. Bagby State Park boat ramp on Lake Walter F. George, which is a 1,200-acre lake that spans across Georgia and Alabama. This boat ramp is reportedly wide enough to accommodate multiple watercraft launching at the same time.

It is always best to consult with local authorities or visit official websites for the most up-to-date and accurate information on boat ramps and their regulations.