Wash swordfish steaks, pat dry with a paper towel and place inside a large zip-lock plastic bag (or covered dish).
In a small bowl, mix together lemon juice, water, olive oil, garlic, salt, pepper, and cilantro (or parsley).
Pour lemon marinade over swordfish and seal bag (or cover dish). Place in refrigerator. Marinate fish at least one hour, but no more than 12 hours; turn the bag occasionally so marinade covers fish.
Prepare grill (medium-high heat) and oil the rack so fish will not stick. Place the fish on the hot grill and cook 4¬Ė5 minutes per side or until fish flakes easily when tested with a fork.