Remains

Remains are blocks found in the Dead Marshes biome, but are often hard to get to due to their tendency to spawn underwater.

Loot
When dug with any type of shovel, remains will yield all sorts of loot. This includes all types of bones, silver coins, gold or silver nuggets, skeleton skulls, and ancient items.

Of course, the material that the shovel is made out of affects the digging speed.