BAINBRIDGE1 rightly questioned Gero's2 data and calculations on the swimming performance of a great barracuda (Sphyraena barracuda (Walbaum)) measured at Bimini, Bahamas, British West Indies, but suspicion was cast on the wrong datum. He doubted the validity of the swimming speed measurement of 12.16 m/sec or 10 body-lengths/sec for a 121.6 cm fish weighing 9.08 kg. This measurement must have been made on a swimming burst, since non-feeding solitary adult great barracudas which I have observed at Bimini either hover motionless in mid-water or slowly patrol their territories, visiting each location at nearly regular intervals. The great barracuda's burst speed is substantially less than the burst speeds of yellowfin tuna and wahoo of approximately the same body length which were measured by Walters and Fierstine3, so there is no particular reason to doubt Gero's measurement. Gero stated his fish had 1.816 kg of propulsive muscle, however, which is 20 per cent of the body weight. Bainbridge accepted this figure, although such a small muscle mass is otherwise unheard of among active epipelagic and littoral actinopterygians.