The new buoys are there so you can get it fixed into your brain what 150' really looks like. Go to a town dock and fixate on one

On the water, and as time passes, it may be hard to remember what you saw so you can use some algebra* (yes, there is a real life use for that stuff

) to refresh your estimation. Recall that distance = speed x time (didn't hurt did it). A fairly average speed for me is 30 - 35 mph. Let's say it's 34 mph which is the same as 50'/second. So in 3 secs I'll have gone 150'. If you can find something (some debris) relatively fixed in the water you can time your approach to it and thus get refreshed as to what 150' looks like. Get to it before counting 1001, 1002, 1003 and it was closer than 150'. After 1003, it was further away. Using an approaching wake builds in some extra margin because it's moving towards you. Just don't get so fixated doing this when on the boat that you forget to maintain a proper watch

Of course you can adjust your time/count for speeds different from my blundering pace. I'd forget about using a laser range finder or other visual device for just the reasons UTS points out.
ps - Anyone know why they put the new buoys out from the town docks and not out from the launch ramps ?
pps - * Of course we all know the "
2 second rule".