Eli5 What is the story with those 4 armed clocks at swimming pools lanes?

Question

Sometimes they have 4 arms of different colors. The markings with a marking every 5 minute mark, and bigger ones at the 15 , 30, 45, 60 markings…Clearly the markings represent increments of an hour

In: 3

Answer 1

For timed swims for kids in swimming clubs

say 20 of free on the 60. Pick a colour hand (we only have 2 handed ones here) Red or black.

So you go on the Red 60. The kid after you goes on the red 5, the next kid the red 10 then the next on the red 15.

When you get to the other end you look at the clock. Where is the RED? did you make it in time? how many seconds rest do you get? then you go ago on the RED 60.

Other sets might be on the 55 sec, slower drills might be on the 1:10, 1:15 etc.

25m sets might be on the 30 sec, 35 sec, etc.