Boy discovers octopus figurine that fell from cargo ship along with 5m other Lego pieces during storm
The octopus is one of nearly 5m Lego pieces that fell into the sea in 1997 when a storm hit a cargo ship 20 miles off Land’s End, Cornwall. While 352,000 pairs of flippers, 97,500 scuba tanks, and 92,400 swords went overboard, the octopuses are considered the most prized finds as only 4,200 were onboard.
Probably by the degree and type of erosion, I would guess. Sellers and traders of these pieces also likely would have to keep up some level of reputability in order to remain in the market.
You rub against the sand with the tides in a littoral zone for 20 years and see how you turn out. Unless they're making Legos outta diamonds, that stuff is quickly turning into micro plastics.