Monterey Bay Aquarium
Admission is $ 49.95 which seems a bit pricey, but it is good for a whole day and there is more than enough to keep you entertained. The Aquarium also has a " low price guarantee " that will refund the difference between their advertised price and any other offers you may find for a lower price. A few minutes on the internet researching deals might be a good idea.
Cannery Row
This neighborhood, immortalized by John Steinbeck, is a popular stop for Monterey tourists. There is the occasional homage to the famous book, but it is mostly known for its many shops and restaurants. You will be close enough to the seaside for seal watching. This is a good free day, depending, of course, on how much you spend in the trendy little shops.