For Strong Swimmers Only
The Consumerist reports today that if you ask Google Maps for directions from Chicago to London you are advised to 'Swim across the Atlantic Ocean for 3,462 miles'.
You can check out this advice on Google Maps yourself here. The offending instruction comes at step 20 or 21.
Checking this out for myself I found that to get from New York to London Google again advises you to swim across the Atlantic. Even stranger is that in both cases the directions expect you to swim to France rather than England and then Google is rather elusive about how you should get from Calais to Dover. Although a number of people have actually swum the English Channel in the past Google presumably assumes you will be a little tired after swimming the Atlantic and will allow you to take it easy by catching the Calais to Dover ferry instead.