The sunken forests in Rye, New Hampshire are an interesting site when it is rarely visible during extreme low tide events.
The sunken trees were inundated with a rise in sea level and have been carbon dated to ~3500-4000 years old. They can be viewed at a small pullout near Odiorne State Park. There are also some at Jenness beach but these are rarely seen the last time in 2010. An interesting phenomena to see if you catch it just at the right time.