The South Boston waterfront just got a new Irish immigrant, and something tells us it’s going to fit in just fine. M.J. O’Connor’s at the Westin Boston Waterfront (425 Summer Street, Boston, 617.443.0800) is the pub’s second Hub location and joins fellow Briar Group venture City Bar as the latest addition to the Westin’s new ground-level retail space. The touches of the original M.J.’s at Park Square — dark mahogany wood, stone hearths, and hand-painted murals— are present here, but with an airier aesthetic. Guinness tops the impressive beer list, and beer-battered fish and chips is one of executive chef Ben Hennemuth’s menu staples. Irish eyes, you now have another reason to smile.