I thought this couldn't happen

[chuckdelicious]

Well, I was playing a randomly generated map and lo and behold, a one tile island. No vikings in this one, so this is the ultimate defensive position to keep your civ from being obliterated. Well, until someone researches amphibious warfare.

[Jaybe]

You're the Vikings, right?

[Dauphin]

I've done that before.

You can also ring multi-tiled islands with cheap-o units so that they'll be safe for an age or two.