Nosebleeds and shark's sense of smell

[DiveBen]

My son received his open water certification last September. And yes, it is completely awesome having my 16 yr old son as my dive buddy. A bit of a concern for me, is that he is experiencing some nosebleed, since his certification. We are still trying to zero in on the cause and fix, and I think we are both currently convinced that it occurs on ascent. Anyhow, we are planning to hit the ocean starting next month. We have been hitting the Florida springs over the winter, waiting for the ocean waters to warm up enough for our "taste". Should I have much of a shark concern over his nosebleeds? The bleeding is what I consider to be light, and does not continue at the surface. I am not being wiimpy about it, but just want to get an idea of the level of any potential risk.

Also, this one is one I always wondered about : since they say that a shark can smell a drop of blood from a mile (or two) away, then why do you see boats on TV chumming the waters with barrels of blood and fish-heads, waiting for sharks to show up??? Why don't they just go out there with an eyedropper and drop a couple of drops of blood in the water, instead ??? Is the "smell statistic" just theoretical, and not really literal?? Seems like a very small amount of blood in the water would be diluted and overwhelmed, at any significant distance, by many other smells in the water. What is the true bottom line on this shark smell thing ????

 

[Cave Diver]

I'd be more concerned about the cause of the trauma behind your sons nose bleed than I would be about any potential danger from sharks.

 

[Bubbletrubble]

Nosebleeds are very common in novice divers. Read this other SB thread or do a search on SB and you'll get numerous hits.

Divers Alert Network has a FAQ on nosebleeds in beginner divers.

You and your son should check out Dr. Kay's ear equalization video link in my sig.

Although a shark can detect blood in one part per million in sea water, the blood has to actually reach the shark's sensory organ(s). Dissemination of the blood is governed by random diffusion, currents, etc. By chumming with lots of fish blood/heads/guts, the crew is increasing the likelihood that the blood will attract one or more sharks.

Honestly, a little nosebleed due to sinus squeeze, forceful pinching of the nose during Valsalva, or mask squeeze is not going to be enough to attract a shark from a great distance away. The blood would first have to exit the mask, the blood would have to be dispersed in the direction of the shark, the shark would have to be there to sense it and willing to respond to it. Add it all up...and the chances of the nosebleed attracting a shark are very, very, very low.

 

[Code Monkey]

I wouldn't worry too much -- I don't think the sharks are all that excited by human blood. I was on a trip where the last diver out of the water on a shark feed lost a finger on the dive ladder (really sad). She fell and bled in water teaming with bull sharks. None of the sharks came for a nibble.

 

[lemondiver]

Sharks want oil based blood-fish blood. We have water based blood. The only issue is that if there is a lot of blood in the water the shark sees the red color and may come over to check it out. Once they don't smell the oil based they know it's not food. As far as chumming, they use a lot because it has to make a chum slick, you don't know where the sharks are, they could be 50-60 miles away. Nosebleeds are not so common unless something in done incorrectly or something is wrong. That would be way more dangerous than any sharks.

 

[diverdoug1]

Sharks want oil based blood-fish blood. We have water based blood. The only issue is that if there is a lot of blood in the water the shark sees the red color and may come over to check it out. Once they don't smell the oil based they know it's not food. As far as chumming, they use a lot because it has to make a chum slick, you don't know where the sharks are, they could be 50-60 miles away. Nosebleeds are not so common unless something in done incorrectly or something is wrong. That would be way more dangerous than any sharks.

Lemondiver,what is this magical oil based blood of which you speak? OIL BASED BLOOD???????? Erythrocytes won't function in an oil base! OK, sharks do home in on fish oil (which is why I have a DC garberator to grind up barracuda when I chum for sharks), but fish do not have "oil based blood". Armchair pontificating about a subject which you do not understand leads to the spread of your ignorance. The enemy of truth and scientific discovery is ignorance, magical thinking, and firmly held beliefs in mythology. Also, chumming for sharks with mammalian blood does work very well. I frequently have used pig blood to chum when fishing for sharks in the Gulf of Mexico (because I don't know where I can get 5 gallon buckets of fish blood), and they tear up the hams we hang over the side to keep them interested. Sharks eat fish, birds, and mammals. Most are predators AND opportunistic scavengers.

 

[sailingk8]

DiveBen, Once you find out what the problem is and you go below, if your son's nose bleeds and he feels uncomfortable let him call the dive. Regardless of how the shark may or may not react to the trace of human blood, if your son is uncomfortable he won't be having a confident dive.