That's a hard one. Many of the local restaurants serve up good seafood. So I'm listing only the restaurants that specialize in seafood and reflect that in their name. All this info has been collected from online comments at RehobothFoodie.com and my own preferences:
1. Henlopen City Oyster House on Wilmington Avenue in Rehoboth: Consistently good seafood preparation. They are open for lunch in the off season, and one of my pick hits is a bowl of their amazing chowder and the lobster reuben.
2. Big Fish Grill on Coastal Highway: Big, often noisy, some kids mostly well-behaved, and consistently good seafood. Pick hits include the maple-glazed salmon, their shrimp salad and any of their fresh fish specials. They are adjacent to Big Fish Seafood Wholesaler who provides product to a great number of local restaurants. So chances are your dinner was swimming around just yesterday.
3. Fish On in Villages of Five Points and Matt's Fish Camp on Coastal Highway in Tenley Square: Both of these SoDel Concepts restaurants have exceptional seafood. We love the dedicated happy hour menu at Fish On, along with their clam chowder and the crispy/crunchy fish & chips entree. At Matt's, we never miss the clam chowder and a plate of oysters on the half shell. The Fried oysters are quite good too.
4. Fins Fish House in downtown Rehoboth and Fins Ale House on Coastal Highway: These longtime spots are known for a reliable raw bar and for good, consistent seafood. We like any of the fried fish entrees, the oyster po'boy & bacon sub (they call it the Peacemaker) and their tuna salad for lunch. The bloody marys at the downtown location are the stuff of legend.
5. Beaches Seafood in Milton: Don and Lori Allan have what appear to be the very best prices on Alaskan King Crab legs (AYCE in the off season for only around $45 bucks or so!) and salmon. Their crabs are competitively priced, and they do not start steaming them until you order them. So ALWAYS call ahead for crabs in the season!
6. Mason's Famous Lobster Rolls in the ocean block of Rehoboth Avenue: This tiny franchise has a family connection to fresh-picked Maine lobster delivered pretty much every day. It's just a storefront, but the lobster rolls are quite good and served in the regulation-style toasted split-top roll with butter. You can get the cold lobster “salad” style roll or the warm, buttery style. Either way, you will not be sorry.