FINA sets the rules for swimming pools and diving. The international competitive swimming organization, requires its pools to be at least 3.4 meters deep for a 1-meter high diving board. This is about 11 feet for a 3-foot high board. A 10-meter high diving platform needs a pool depth of at least 4.5 meters...pretty danged deep.
Need more information? Newspaper archives are one of the best online research tools.