https://www.vice.com/en_us/article/9kee7y/mysterious-craters-in-the-seafloor-were-likely-formed-by-garbage-scientists-say

While surveying the seafloor off the coast of Big Sur, California, a team of scientists has made a bizarre and depressing discovery: thousands of miniature craters, many of which appear to have been formed by human garbage.

These trash craters, more formally known as “micro-depressions,” were spotted during a series of underwater autonomous vehicle (AUV) surveys led by the Monterey Bay Aquarium Research Institute (MBARI) in 2018 and 2019. Eve Lundsten, who presented the findings at the American Geophysical Union annual meeting in San Francisco today, said the discovery was totally unexpected. The team hadn’t sent its AUVs out to study garbage, but rather to elucidate the origins of a cluster of much larger seafloor craters in the same region that comprise North America’s biggest “pockmark field”.