Crested Pool is a beautiful blue, super-heated pool. Tragically, it is one of the thermal features in Yellowstone to have claimed a human life. It is always prudent to remember the dangers in the thermal areas.
Depending upon your definition of a geyser, Crested Pool is either a geyser or a pool which has periodic large heavy boils. Crested Pool is almost constantly in overflow over its built up, crested, edge. Every few minutes, it has heavy boils. Usually these boils only reach a few inches, but sometimes they reach a few feet. On rare occasions, most recently in September 2017, they reach 6 to 8 feet and have even gone over 10 feet. The larger boils build quickly and usually startle anyone standing nearby. After the larger boils, the pool drops below overflow and takes a few seconds to reach overflow again. These boils can be sufficiently unlike the usual boiling that the "geyser" definition seems indicated, even if "eruptions" are relatively rare.