Psychometric performance of 12 divers was evaluated throughout a series of 60-72-m in-water heliox non-saturation ('bounce') dives using a repeated-measures, within-subject design. Assessments were made onboard a dive tender, using a portable computerized battery within 30 min of the diver leaving the water, 2 h later, and on rest days. No significant decrement in performance was demonstrated either post-dive or throughout the series. Ten controls showed no alteration in performance due to environmental factors such as ship motion. The consistency of the results confirmed the suitability of this system for monitoring cognitive function during a series of potentially hazardous dives.