Looking for sushi, SE Asian, oyster and dungeness crab recs near downtown.
Elliott's during happy hour for oysters, Market Grill for grilled salmon sandwiches (or plates). You can get a good bowl of mussels at many happy hours, like BOKA (my favorite), Maxamilien's in the Market (best view and cheapest) or the Brooklyn. The Brooklyn is good for oysters, too, but I do like Elliot's better.
You should be able to get a good crab at one of the Chinese places in the International District but I go to the 'burbs for my Chinese these days, so I'll let someone else give you a current recommendation.
1509 Pike Pl, Seattle, WA 98101
Jack's Fish Spot in the Pike Place Market would be a good bet for you. They are about as far from fancy as you can get and they have good fresh seafood. It's a fish and chip bar with fresh crab and oysters also on the menu. If you are in the Market it's a great place to grab lunch.
Elliott's Oyster House for Happy Hour would be a good bet, too.
Jack's Fish Spot
1514 Pike Pl Ste 2, Seattle, WA 98101
Elliott's Oyster House
1201 Alaskan Way, Seattle, WA 98101