The diffusion of particles on a random sea surface, due to the random fluct
uations of the Stokes drift velocity, is examined. Experimental results are
presented for the diffusion of particle pairs on the surface of a three-di
mensional random sea with a Pierson-Moskowitz surface spectrum and a cos(2)
spreading function. The results show good agreement with theoretical predi
ctions, particularly at low separations where other affects are negligible,
Diffusion of surface particles in different sea states is also discussed.