The top picture is very interesting. The vessel in question obviously sank and was covered relatively quickly. That would seem to be the only logical explanation for the uniform angle of the cannons protruding from the sand.
Also interesting is the fact that the wreck is in the present day surf line---yet it was apparently unsalvaged. Lots of old derelict hulls wind up beached, but usually they are stripped and are mere hulks...I am not sure I have ever seen anything quite like this (of course my experience is severely limited).
It would be interesting to do some research to figure out what series of events got the vessel into that location more or less intact, yet also allowed erosion to uncover her.