Hao Ren fully appreciated the differences in the values of different races. Differences were even more apparent when it came to the sirens. No matter how close the deep-sea "fish" looked like carbon-based living things, they were essentially elemental creatures. The most significant difference between elemental beings and ordinary life was in their perception of the material world. At least one-third of the gifts that the Queen of the Sirens brought was rubbish, but Eva still appeared happy.
There was even a piece of rotten, steel-toe shoe, which some siren must have picked up while strolling along the beach. In Katreina's mind, the shoe was a marine object, and she had begun to instill this idea in Eva.
Based on the sirens' thought process, everything they found in the sea was a marine object, including floaties, bottles, offshore drilling rigs, and Jack who sank with the Titanic.