Lead Belly

Lead Belly is a Fallout 3 Perk.

With the Lead Belly perk, you take 50% less radiation every time you drink from an irradiated water source.

Note
Lead Belly is one of the most useless perks in the game along with all others that affect radiation, simply because its so easy to completely remove all rads for 100 caps or even for free in your house (for a small investment).

Trivia
The perk is likely named after the 1930s and 1940s musician.