There are many wines that go with shellfish. As a rule of thumb look for crisp dry whites.
Mussels & crab - opt for a Muscadet, Sauvignon Blanc or a dry Riesling.
Lobster - go with a classic Chablis, good white Burgundy, New World Chardonnay or Chamopagne.
For oysters and scallops, again go with a good Chardonnay, though light reds can work too.