"We need to hurry, the sea water is rising!"
After toiling away for half the day, the family was actually already exhausted, but they clenched their teeth and could persevere.
The reason was simple,
If it were a 100-pound rock, most people would definitely complain about fatigue, but, if it were 100 pounds of gold, and it was yours to keep once transported, then most people would definitely start running.
Moreover, based on past experiences from watching movies, the items in these kind of treasure chests, the least valuable tend to be gold.
Of course... no one knew what was actually inside until the treasure chest was opened.
It could be heavy with all sorts of treasures.
Or possibly just a pile of large rocks.
By the time they moved the fifth chest, the sea had risen, soon submerging the deep pit completely.