Lifeguards are not that common in India in my experience, but I avoid tourist beaches where they will most likely be. If your friends cannot swim, or if they cannot swim well, they should avoid taking any risks in the water. Even if there is a lifeguard present where you are, theres no guarantee that they will spot one individual person in trouble in the water, particularly on a crowded beach. Tides and waves can catch out the most experienced swimmers and no-one is 100% safe once they are waist high in water, so your friends should be sensible and responsible when they are near the sea.