Undergraduates from chemical engineering, applied chemistry, and environmental science courses, together with first-year postgraduate research students in electrochemical technology, are provided with an experiment that demonstrates the reduction of dissolved oxygen in aerated seawater at 25°C. Oxygen reduction is examined using linear sweep voltammetry (i.e., the recording of steady-state current vs. electrode potential curves at a constant potential sweep rate). The use of forced convection to a smooth, rotating disc electrode (RDE) of 3.8 mm diameter (area = 0.113 cm[superscript 2]) in laminar flow provides control of the rate of mass transport of dissolved oxygen toward the cathode surface. The use of rotation speeds in the range of 200-9500 revolutions per minutes (angular velocity of 20-1000 rad s[superscript -1]) allows a linear (Levich) plot of limiting current vs. the square root of rotation speed to be made. From the slope of this plot, the diffusion coefficient of oxygen can be calculated as (1.5 ± 0.2) x 105 cm[superscript 2] s[superscript -1] at 25°C.