There was also the coveted blue band, which you could only get by doing a very rigorous set of tests and passing junior lifeguard training. I had to swim who knows how many laps and tread water for like an hour, plus lift bricks up off the pool floor and various other lifeguard-related things. The blue bands were super "rare" and I realize now it was just an inventive way to encourage the kids to swim better and harder.
Not exactly the same bands you were talking about, but a cheaper alternative and a good way to keep control and prevent drownings before they happen.
Almost two decades passes. I'm in Bali, on a deserted beach with my ex because we "don't want the average experience" or whatever. A small argument and I decide I want a swim. I walk out through the surf, my mind overcome with thoughts of the pathetic argument. I don't think about the undulating sand beneath my feet, but I should. Not even 2 minutes into my swim and I'm out a good 200m. I've swam 10km before in the sea, I'm fit enough, but I had been in a bicycle accident and fractured my dominant arm just 8 weeks prior. My natural confidence, my training, my accolades had resulted in my taking an unknown sea for granted. I looked to the sure, my girlfriend had vanished, no doubt going to lick her wounds from our previous verbal exchange.
I can honestly say the human mind is a strange thing under pressure. I thought back to being 12 and outright laughing at the tourists (emits, slang for ants in Cornish) who died every year often through a mix of alcohol and poor planning. The realisation of such past hubris was overwhelming. I also realised that the people I knew from there would be laughing at my death. I was now well over 1km from shore. My mind kicked in properly, I started swimming hard normal to the rip tide. After 5 minutes of treading water and thinking hard some rocks where looking achievable, so I decided to give it all in the hope of getting there, a fast sprint was my plan and thankfully this worked.
If ever I thought I'd given 100% to a physical activity before I was mistaken. My legs bore the brunt of this assault, my upper-body was uncoordinated due to the cycling injury. My watch was telling me I had been hard going for barely 10 minutes. I was not even half the way, my fear I think allowed for adrenaline to kick in, I was at this point making peace with death of drowning, as an asthmatic a death that has always scared me.
I made it to the rocks and to my joy I didn't need to climb along them, the rip tide was no more. I made it to shore. A half hour swim that had been like no other I've ever had and I hope will ever have. I was so upset with my ex for leaving me. Not watching nor caring as I had asked and she agreed. Going into the unknown water without someone aware is folly and I thought she would be observing me. Anger and most likely just bordem resulted in her not doing so.
TLDR: I was a good swimmer, I still so very nearly killed myself. Knowing when someone is in trouble requires education.
as an engineer, I assumed this ('normal') meant across/perpendicular/90 degrees to the rip tide, not against it ...
I believe 90 degrees to a rip tide is the correct thing to do ...
Also, a back-float is always generally a good strategy in salt water conditions when you've lost control or strength to swim. You carry over common waves and it takes very little energy.
Honestly, it sounds like you panicked.
The parent does mention swimming against a rip current, which would explain the need to swim at maximum physical exertion for an extended period of time. In that case I don't think he panicked.
Huh? Why are people writing this? You don't swim against a rip current.
It's a really smart idea, and while even an excellent swimmer can become fatigued the more experienced ones will be less likely to need aid than the less experienced ones.
I do work in this field (wireless vital signs monitoring) and unfortunately I don't know of any current technology that I would trust to monitor heart rate on a swimmer other than perhaps a chest strap (but not as a safety device either). For a point of reference, the Apple watch fails to accurately record heart rate when very sweaty or experiencing periodic movement (such as the periodic arm waving).
There was a kickstarter project for a swim safety device (mentioned by others in this thread) but I believe that was based around picking up the arm movement characteristic of this response, which may be a sensible approach (I don't know enough about the characteristic motions of the drowning response vs regular splashing).
A device for alerting for a drowning subject would be classified as a medical device (in Europe most likely class IIb as it is measuring a vital function in a life support scenario) as the malfunction of the device could fail to prevent the saving of a life. The burden of certification of such a device is understandably high, and one would have to be able to demonstrate that the device can accurately and reliably measure in its intended use and show that any risk that it doesn't has been adequately reduced (I'm simplifying greatly).
Unfortunately it's basically impossible to test, after all how would one get ethical approval for exposing subjects to conditions of near-drowning, so one would be dependent on placing prototype devices on swimmers and catching episodes of near-drowning by chance. It would take a considerable length of time to gather sufficient data to confirm the reliability of the device under such conditions, obviously...
(and no, I would not consider it appropriate to test the device under general swimming conditions as these would not adequately predict performance under drowning conditions).
In terms of cost, an earlobe pulse oximeter doesn't have to be more expensive than a fingertip one (aside from some miniaturisation costs perhaps) but part of the costs of these devices is due to patent issues: http://www.law360.com/articles/106524/philips-accuses-pulse-...
It wouldn't be able to interface with a device the lifeguard has in this case, but it could surely start making noise and/or flashing in an emergency.
There's two things that such a device would need to have: quite low false positives (so that the lifeguard isn't distracted by false alarms - leading to a boy-who-cried-wolf scenario), and vanishingly small false negatives (the first time a kid dies because the device didn't work, it'll be a bad day). In-water RF would be very hard to do to make those two conditions true.
Edit: Don't get me wrong, I think it's a fabulous idea. Wearing my EE hat though, I haven't thought of a good way to do it that would work reliably enough for a life-saving device.
Maybe that's not such a bad thing overall though.
Followed shortly thereafter by "I wonder where you get/how you generate a dataset of the vital signs of drowning children..."
panic attack data set will get you halfway there and panic attacks happen naturally and sufficiently frequently. Add the dataset from something like asthma attacks (unfortunately it is easy to obtain too).