Examples:

• There's no point worrying about it - we'll both be six feet under by then.
• Today, in English class, we had to write an essay about what other people will say about us when we're six feet under.
• You'll be six feet under when Mom finds out that you dented her brand new car.
• If you keep drinking and driving you're going to end up six feet under.
• The way I see it, hoarding all that money won't do you any good once you're six feet under.
• Everyone celebrated when the dictator was finally six feet under.
• He owns his own shop, called Six Feet Under Tattoo Parlor.
• All the money in the world isn't going to help you when you're six feet under.