Did they sound like loud fans ? This is almost certainly what you saw. The C130-J is flown by the RI ANG, out of Quonset, and that is where they fly : Pt Judith to Beavertail to Newport to Westport and the Islands. The J model is the latest major revision and is much more silent than previous. Clammer and I were fishing on his boat off Jamestown when they came over the island and passed over us. Zero sound then we were awash in bright light, then the sound came.
C130 (sounds like a louder fan and most likely because that is where they fly, dead silent until they pass you too)
Here are special mission 4 Js