Yes, this might be something you should worry about.
The bottom line is that I believe you may have been experiencing conditions leading to shallow water blackout. If it happens again, do not panic or breath deeply, just relax and get out of the water. Get some one to assist or watch you get out in case you pass out. Physical activity, like swimming, might help reverse the effects (but I don’t know for sure). You can also close your mouth and one nostril and breathe through the one open nostril. Or breathe into a paper bag or something similar. Sound weird? Let me explain...
Tingling in the fingers and hands is a symptom of lower levels of CO2 in the blood than normal (HYPOcapnia). This is often caused by heavy, deep, or rapid breathing (HYPERventilation) combined (I believe) with low physical activity, which causes you to expel more CO2 than your body produces.
The tingling fingers happened to me twice. The first time was self-induced a few years ago when I felt exhausted after shovelling snow. While resting afterwards, I felt like I needed more oxygen so I started breathing deeply, which eventually caused my hands to tingle, which made me think I needed more oxygen, which made me continue to breathe deeply, which made things worse, until my hands started cramping and seized up (tetany). By then I had been driven to the hospital, where the triage nurse immediately gave me a paper bag to breathe into and everything improved within a few minutes. Turns out I felt exhausted initially because I had pneumonia, but that’s another matter. The point is that the tingling and the hypocapnia (low CO2) was likely caused by my deep breathing (hyperventilation) while resting.
The second time I felt the tingling was the day before yesterday, after an hour or so of snorkelling in a shallow but murky lake, which kind of gave me the creeps (anxiety?). Later I wondered why my hands would be tingly, and then I remembered the time they felt tingly from my self-induced hyperventilation. This led me to think that the tingling had something to do with the way I was breathing through the snorkel - perhaps breathing nervously, or taking deep breaths or holding them too long without realizing it. This led me to search online for more clues. That’s when I found this discussion page. The tingling you experienced sounds like what I experienced.
I did more searching and that’s when I found out more about hyperventilation, hypocapnia, and shallow water blackout. Since no one else has mentioned hypocapnia or shallow water blackout in this discussion, I felt compelled to join this forum, and post my thoughts. Even if hypocapnia is not what caused your tingling, it is worth sharing, for everyone’s awareness and safety. I am not a medical professional, nor a SCUBA diver, so I could be wrong. Just consider what I’m saying, do your own research, consult with professionals, and draw your own conclusions. I’m just trying to do what I can to prevent something bad happening.
Here is my understanding of how shallow water blackout works, in a nut shell. When you hold your breath for a long time, your body will eventually react by gasping for air. This increasing urge to breathe is actually not induced by a lack of oxygen, but by a build up of CO2. That is, a larger build up of CO2 in your body creates a stronger urge to breathe. The flip side of this is where it gets problematic: when you have less CO2 in your body, you have less of an urge to breathe - even if you need to breathe! This in turn, makes you feel like you can hold your breath longer than you should, or breathe less than you should, and if you keep holding your breath or breathing less, you black out (lose consciousness) from lack of oxygen. If you’re in the water when that happens, you’re in big trouble. It is also worth noting, that you do not need to be in the water or at depth for this to happen.
You can read more about it here:
Freediving blackout - Wikipedia
The connection with hyperventilation is that hyperventilation (especially with low physical activity, I believe, like casual snorkelling) reduces the amount of CO2 in your body, which can cause tingling in the fingers, and make you feel like you don’t need as much air and oxygen as you actually do. Note however that the absence of tingling does not guarantee that you have enough CO2 in you!
The weird thing about my snorkelling episode is that I may have been hyperventilating without even realizing it. Maybe this or something similar is what happened to you in the pool.
For the record, about six hours after feeling the tingly fingers from snorkelling, I felt considerable aching inside and around my shoulders. I have felt this once before, and I think it was after hyperventilating during my pneumonia episode, but I don’t remember for certain if that’s when I felt it. I wonder if this had something to do with the balance of CO2 in my blood at the time, not unlike the effects of decompression sickness (which I have no experience with). I felt fine the next day.
