We used a strobe tethered to a weight as a rally point in Bonaire for night dives. From the shore, it was easy to see the divers' lights and that strobe from many hundreds of feet away at night. But the slant range only included ~40' of water.
Despite 80' vis during the day, at night we couldn't see the strobe as a rally point directional aid further out than 200-300 ft, altho' as we swam to where we thought it was, it indeed came into view at 200-300 feet, so maybe we were indeed picking up a hint further out.
But as a "which way?" assist if your nav is way off, or you get turned around, it's not much help. More like "alter course that way" when you're heading back and are not seeing familiar landmarks in the dark as you get close to where you think home is. Then it'll help you at the end.
But in daylight? Underwater? No, it won't help at all.