Peel husks and cut off stems of tomatillos. Slice jalapeño lengthwise, remove membrane and seeds. In medium saucepan, combine tomatillos and pepper. Cover with water. Bring to boil. Cook 15 minutes; strain well.
Allow tomatillo to cool 10 minutes. Remove skins.
Using blender or food processor fitted with steel blade, purée tomatillos, jalapeño, salt, and garlic until smooth.
Spoon mixture into large skillet, cook 2 minutes over medium heat. Add water and cook additional minute.
Transfer salsa to serving dish. Garnish with cilantro.