Iron is generally 8 times denser than water, however, humans have built boats (ships) with tens of thousands of tons of iron (and other materials) that can stay afloat (assuming there are no icebergs nearby). An example of this is the 70,000 Tons of Metal which is a metal festival cruise. Whereas a block of iron would sink, an iron boat/ship, like the 70,000 Tons of Metal cruise ship, floats because a boat of iron weighs less than a lock of iron. Gravity affects objects in the shape of a boat less. the iron is reshaped so that it displaces more water than it does as a block. Gravity ain't got nothing on the spirit of metal \m/