Here's something funny I was sent by a friend:

Go to maps.google.com.
Click on "Get Directions".
Enter "Boston, MA" in the left hand box, and "Dover, UK" in the right hand box.
Hit "Enter" or click "Get Directions".
Take a look at instruction #9.

Well, naturally! How else would one cross?

But the funny thing is, they tell you to land in France (at Le Havre), then drive up the coast to Boulougne-sur-Mer, then drive off the dock and across the Channel. Why not swim that part too? That part is actually swimmable, after all...