A 10 year-old boy, who was temporarily buried in a tunnel collapse on Seabright State Beach over the weekend, came back yesterday to thank his rescuers. Although Fresno resident Jack Boldt had to be resuscitated once he was hauled out of the tunnel….and was hospitalized for a time….he appears to have come through the ordeal physically unscathed. Beach-goers are encouraged never to dig holes deeper that the knees of the smallest member of their group….and to never build tunnels or caves….because although the sand tends to be moist and easy to work with in the mornings, it tends to dry out during the day and get crumbly….which means it can easily collapse later in the day.