We usually take the Cape May - Lewes Ferry when traveling between New York/New Jersey and the Eastern Shore. It's an excellent way to avoid some traffic and give yourself a break in the middle of your trip. Cars and trucks line up to make the trip, so a reservation is recommended in the peak summer months. The 18-mile trip takes about 80 minutes. Here's the official schedule and fares.
On the New Jersey end of the Cape May Ferry, the roads and well marked and easy to navigate. Things aren't good on the Delaware end ... they don't have decent signage in that state. Plan ahead with a map and you'll be fine. See the Cape May Lewes Ferry on Google Maps.
The Lewes Cape May Ferry likes to promote itself as very comfortable, but we never seem to get the upgraded ship. And the food's not very good, so you might want to bring your own food and drinks.
If you easily get seasick, you might have a little trouble with the ferry. It does rock a bit. Only the most sensitive stomach will have a problem.
Overall, the Lewes Cape May Ferry is an interesting and worthwhile way to get to the Eastern Shore. It sure beats driving the highways around Philadelphia.