[AndyS]

You need to read about the the so called "artificial reef" they did i Florida years ago using tens of thousands of used tires. Now they are trying to remove tens of thousands of used tires from the ocean floor because it was such a disaster.

Osborne Reef is an artificial reef off the coast of Fort Lauderdale, Florida. Originally constructed of concrete jacks, it was the subject of an ambitious expansion project utilizing old and discarded tires. The expansion ultimately failed, and the reef has come to be considered an environmental disaster—ultimately doing more harm than good in the coastal Florida waters.

In 2007, after several false starts, cleanup efforts began when the United States military took on the project. This cleanup exercise provided the military with a real-world training environment for their diving and recovery personnel, coupled with the benefit of helping the Florida coast without incurring significant costs to the state. In 2015, a civilian corporation took over, and had removed one third of the tires by November 2019.