Lake Arrowhead Mounds

Reader Rob Sirois writes:
Since you’re on the subject of mounds & structures in lakes;

In early June of 2009, my son and I went fishing in a canoe on Lake Arrowhead in Limerick. Our luck with the fish was not all that good. So, we decided to explore some of the swamps and backwater areas. As we passed through a channel I noticed a number of small islands rising abruptly out of the shallow water. Each island seemed much too regular in size to be natural. I wondered if they were man made, perhaps Native American mounds. Centuries ago Lake Arrowhead was nonexistent; it was formed when a hydroelectric dam was built across the Little Ossipee River. It’s certain that the area around these islands was once dry land and these islands were mounds of some sort.Three of these mounds are roughly ten to fifteen feet high and about twenty to twenty-five wide. Two other mounds are nearly half that size, and there may be a sixth mound in a swampy meadow which made it hard to determine size. All seem to be somewhat circular when viewed from above. After my son and I got back from our trip, I searched Google Earth to get another perspective on what we had come across. What I saw convinced me that we had come across some man made structures, I just don’t know for sure if they’re Native American.