Coral Boulder

This sponge-sized brick is actually desiccated
chunk of living coral. When exposed to 1 gallon of water, it expands into full-sized boulder within 1 minute. A fully expanded coral boulder is an irregular sphere 3 feet in diameter. An expanded boulder has hardness of 7, has 55 hit points, and weighs 8 pounds. Water in coral boulder slowly evaporates if it's left in a dry environment, & the boulder shrinks back to its original size in about a
week. If drop in water, coral boulder sinks straight down, & i