Did it look like this guy?
File photo, not mine
According to F&G:
The biggest of New Hampshire's weasels is the RIVER OTTER, at 25 to 40 inches long. These stately creatures of the water are dark chocolate brown in color. Otters may roam as much as nine square miles. As with mink, fish and crayfish make up the majority of their diet. Like other weasels, otters are rarely seen, despite their abundance. The otter sign that I frequently see is where they slide along the snow in the winter