Why do the swimmers (who presumably are excellent at swimming) have these floaty things attached? Obviously so they don't drown but where does that risk come from?
I've heard in open water swims you can get kicked accidentally - is that the major risk? Is it heart issues from cold water?
Look up ‘tow float’. They are useful for many reasons, lots can happen in the water particularly dark outdoor deep spaces with lots of people and things splashing and obscuring visibility.
Tow floats are common in all open water swimming, e.g. triathlons.
I've heard in open water swims you can get kicked accidentally - is that the major risk? Is it heart issues from cold water?