The coastline of the eastern U.S. changes....slowly.
The amount of water in the oceans does change over the long term. During the last Ice Age, sea levels were lower, which allowed humans to cross over to North America from Asia at the (now underwater) Bering Strait.
During colder climatic periods more ice caps and glaciers form, and enough of the global water supply accumulates as ice to lessen the amounts in other parts of the water cycle. The reverse is true during warm periods. During the last ice age glaciers covered almost one-third of Earth's land mass, with the result being that the oceans were about 400 feet (122 meters) lower than today. During the last global "warm spell," about 125,000 years ago, the seas were about 18 feet (5.5. meters) higher than they are now. About three million years ago the oceans could have been up to 165 feet (50 meters) higher.