Digging

The Sims
When on vacation, a Sim can rent a Metal Detector from Rental Shack Zack and go looking for buried treasure. Once the Sims stops looking for treasure, the metal detector returns to the shack and must be rented again if if the player wants that Sim to keep digging. More often than not, the Sim will find small amount of money that was presumably lost by other vacationers. However, Sims may find souvenirs while looking for treasure. If they're lucky, they may even find a bit of treasure. Of course, they may also find an old boot or two.

With Unleashed, a bored dog may dig holes. Since vacationing families take their pets with them, there's a slight chance that a dog will dig something up while on Vacation Island, but it's not very likely.

The Sims 2
Digging is an interaction for The Sims 2, added in The Sims 2: Bon Voyage. Digging can yield unexpected treasures, maps to secret lots, geysers etc. Sims can dig in sand, dirt, or any other natural substance. Geysers sprout up out of the ground for some unlucky Sims, creating puddles that lower the environment need, and cause weeds to sprout.

Dogs can also dig holes in the yard with the addition of The Sims 2: Pets. If you move the holes with move_objects on it causes a blue space where the hole was. (only with Pets)