We stay at Narrows Too... they have FHU. You can kayak right off their property in Mt. Desert Narrows... it's pretty protected. We also go to Salisbury Cove on Eastern Bay , Indian Point and Pretty Marsh on Western Bay. All are salt water and pretty well protected.
There are numerous ponds/lakes in the area that we like to paddle in. Somes Pond,Eagle Lake,Jordan Pond,Long Pond,Echo Lake are some of the ones we've been on.
We will be heading up again in June and stay until late August. Yes, it does get pretty crowded at times and at certain attractions, but not unbearable.