If you're one of the countless tourists planning to hit up a Hawaiian island this summer, this story will certainly alarm you. Honolulu Magazine reports that more than 20,000 pieces of marine debris were found on Hawaiian shorelines during an aerial survey conducted last year. The study was undertaken by the Hawaii Department of Land and Natural Resources and the University of Hawaii at Mānoa’s Hawaii Coral Reef Initiative.Plastic comprised the bulk of the litter, as well as fishing, boating gear, and even sea vessels and abandoned shipping containers. Tires, floats, and buoys appeared to have been discarded by humans directly into the water and on the beach.Niihau was the biggest offender, with 38% of the total litter found on there Oahu had the least amount of waste, comprising 5% of the total. The study also determined that the garbage had little connection with the 2011 Japanese tsunami, which had been thought to have carried waste to the island. It seems that the real problem is human carelessness.These photos document the extent of the damage.