Pappy always said to stay out of the river

A few ticks ago, I took a trip to New Orleans. I had visited on the ground once before to go to a Page Plant concert, but this time I visited from above via Google Satellite. The river, which I assume is 'the' river - the Mississippi - but I could be wrong - was quite intriguing and I began to follow it. I stumbled upon the below. What are those things in the water? Trash? Looks pretty big for that in my opinion. They just look odd to me and I can't really think of anything they might be.