Is it true that the land really close to most banks is a good place to look for buried treasure?

Yes! Did you see the movie "The Bank Job"???

well, things are commonly lost in the water and currents can carry them to the shore, and waves will push sand and small sediments with the object, eventually berrying it; ppl love to go to the beach and drop things of leave things behind and the items will be lost in the sand. So yes, the shore is a good place to find treasure, but the term treasure has a vague meaning (a chest of gold to shells to jewels or what have you).