On January 19, an unusual clustering of impulsive hydroacoustic signals (T-phases) was observed on recordings from SOFAR (Sound Fixing and Ranging) channel hydrophones located near the island of Oahu, Hawaii. Accompanying these randomly distributed T-phases was a continuously elevated level of background noise. The most intense activity began around 10 hours UT and lasted for about 1 hour (Figure 1). Since these characteristics are typical of submarine volcanism (see “Submarine Volcano,” Eos, November 7, 1989), a message was sent to the National Oceanic and Atmospheric Administration's VENTS Program (Pacific Marine Environmental Laboratory, Newport, Oreg.) advising of possible submarine volcanic activity.