Today military aircraft are trained to land not only on smooth tarmac, but also on grass or even on sandy beaches. here is one training exercise in Pembrey Sands Air Weapons Range. The beach is long and when the tide is out very wide it is ideal for Natural Surface Landings (NSL). So a Lockheed C-130J Hercules C.5 can easily land. The ground control team marks out the runway with day-glo orange banners. A rectangle of four banners is approximately 100 yards by 60 yards indicating the touchdown point. Three fire engines and support vehicles were positioned at the mid-point (something which probably wouldn't exist in a real mission). It required 5 approaches with the last one being successful for the C-130 to land.
Full album is here: Lockheed C-130J Hercules beach landings