You'll need to take the Peak's Island ferry for Portland. Once
you get to Peak's the cache is a little less than a mile from the
ferry. The web site for Casco Bay Ferry Lines, including ferry
schedules and charges is here.
At the top of the street, make a right and follow the road
around to Whitehead St. Make a right onto Whitehead St. and another
right onto Seashore Ave. This will bring you closest to the water.
Stay on Seashore Ave which will eventually bring you to the general
area the cache is located.
For those of you who do not want to walk, there is a bike rental
shop not far from the ferry landing. (Go to the top of the hill and
make a left, shop is down the street and on the right hand side of
the road.) Many visitors like riding around the island.
For kayakers, the shore is accessible only from low to mid tide.
You'll not be able to easily land in rough water or at high
tide.