It looks like what you have there are some old freighter keels. I would do what Mackaydon suggested and try to find an identification before wasting your time searching.
There are a number of possibilities here. First, the ships could have been destroyed while at anchor. This is known to have happened in the past in other areas. A fire starts on one ship and spreads to the others.
Second and most likely, they could have just been derelict ships that were eventually disposed of at that location.
Above all else, given how far inland they are, if the ships did carry anything of value and were somehow wrecked, they would most likely have been salvaged shortly after they were lost.