Despite recent advancements in diver communications, there is little information on the ability of divers to use a multi-function head down display (HDD) or head mounted display (HMD) for routine underwater tasks. Three information displays (HDD, and a monocular and binocular HMD) were tested by nine mine counter-measures (MCM) divers at the surface and during simulated dives to 42 metres in 6 deg C water. Divers used the displays to report depth and alarms and to perform navigation, object location and target identification tasks. Task performance was analyzed for speed and accuracy. Subjective data were collected on the usability of the displays in conjunction with other MCM tasks and equipment. Performance was slower and less accurate (p0.05) at 42 msw than at the surface. At 42 msw, response times were faster (p0.05) when using the HDD to report depths and locate objects; otherwise there were no significant differences between displays. Subjective data showed a slight preference for the HDD. Some divers reported eye fatigue or nausea when using a HMD. Although MCM divers were capable of using both the HDD and HMD effectively during dives to 42 msw, each display presented unique design and usability problems.