Eastport is a delightful US city with lots of history, and great scuba diving. There are a few dive sites, but the most popular must be the "Old Pier" which is directly accessible off Sea Street. The dive site has the remnants of a late 1800's pier that yields a variety of marine life and bottle scrounging, and a couple of nearby reefs are there as well.
There is also a dive off Dawson Street, which although smaller in scale.. the marine life can reach the density of life at Deer Island.