Today I took a walk from my house to the beach at Plum Island. I met my wife and kids there who took the car along will all the beach stuff.
I was armed with a water bottle and an IPOD and a letter which I deposited at the Post Office.
Along the way, I passed many tourists, A-frame signs, and one clam shack--all that Newburyport has offer. Another policy thought (and I know it's better than it was years ago): it is not all that safe to walk out to the Island.
There's Google Map 'mashup' at http://www.gmap-pedometer.com/ which you can use to measure walks, runs, bike rides and auto trips. It's pretty cool. You can save your 'routes' for future reference.
Here's the 5.3 mile route I took:
If you click on the satellite view, you'll see a lot more beach at the center of Plum Island than there is now.