KTA, we live in a great place with lots of choices for diving. That's the good news, the bad news is most of them are colder than you can imagine, visibility sux and there's not much to see. Other than that it's great. Only kidding.
You'll get introduced to the Nubble first (great site but very cold water), then Fort Foster (warmer water but not very deep) both in Southern Maine. After you finish your out dives get down to Cape Ann in Mass. Best variety and there will always be a lea side of the island to dive (not always true in Maine). That's the good news, the bad news is the parking Nazi's that inhabit Cape Ann, sometimes a parking ticket is the price we pay.
As far as the lakes are concerned they are easy and generally warmer. There's not much to see and you have to be careful which lake you choice, avoid tea lakes (water the color of tea = no visibility), watch the thermoclines (gets very cold the deeper you go), and watch the boat traffic (fresh water sailors do not have a clue about dive flags).
Best of luck and don't be in to much of hurry to buy equipment. Rent before you buy.