Boston Harbor Cruises runs whale watches from Long Wharf out to Stellwagen Bank from April through October — the most reliable way to see humpbacks, fin whales, and minkes in New England waters. Three-hour trip; bring layers (it's cold even in August once you're 25 miles offshore). New England Aquarium narration on board. Adults 21+: cannabis isn't permitted on the boat (BHC is a private operator running on federal waters at points), but the post-trip walk back through the North End includes plenty of dispensaries for sealed-product purchase.