These are riverside, not oceanside.
Black Cow Tap & Grill: Waterfront dining (deck) and bar. Good food. Seems to be a popular watering hole.
Michael's Harborside: Same
Michael's is just east of the Route 1 bridge across the Merrimack River. The Black Cow is about a block further east; turn left at the traffic light.
On the opposite side of the Route 1 bridge is Striper's Grill. I've never been, but they have riverside dining.