  In the Daya Bay Reactor Neutrino Experiment 960 20-cm-diameter waterproof
photomultiplier tubes are used to instrument three water pools as Cherenkov
detectors for detecting cosmic-ray muons. Of these 960 photomultiplier tubes,
341 are recycled from the MACRO experiment. A systematic program was undertaken
to refurbish them as waterproof assemblies. In the context of passing the water
leakage check, a success rate better than 97% was achieved. Details of the
design, fabrication, testing, operation, and performance of these waterproofed
photomultiplier-tube assemblies are presented.
