Yes, that is motion blur.  I had just run up the hill from taking the site survey pictures to see Brendon telling everyone how to pose like superman.  (Critical Information for any Diving Trip.)  F5.6 is the largest aperture for the at 70mm.

Date:	Saturday, July 25th, 1998
Film:	Fuji Nexia APS 200 (print)
Lens:	Nikon 24-70mm f/3.5-5.6 IX