Misconceptions and Fallacies

[Rick Murchison]

I understand the science behind it. They can pick up any smell from that distance. Here is the rub though. Humans are not on their biological food menu and therefore do nothing for them smell wise.

I'm sure the crew of the Indianapolis will be glad to find out it wasn't their blood that got 'em eaten.
Now I've personally witnessed sharks showing up to check out bloody pork and bloody beef, even caught a few over the years using both. Haven't tried human yet, but suspect they'd check that out too.
While other-than-fish blood may not indicate the presence of the usual fare, some sharks do like mammal, and all the big bitey ones are pretty egalitarian in their flesh selections, if it's an easy target. Bottom line, I think your "do nothing" is at least as far off base as the "instant frenzy" fallacy.
Rick

 

[Charlie99]

I'll weigh in again on the well beaten overweighted diver air consumption topic ......

Several times I've had newbie insta-buddies that hoovered down their air really fast on the first dive. In a lot of those cases, they were clearly negatively buoyant for most of the dive and finning heavily even when we were going slow. When they asked how come I still had more than half a tank left at the end of the dive, I'd explain to them how to stop finning and adjust their BCD. In almost every case, it made a large difference in their air consumption. A frequent comment was something like "wow, that was a lot easier, I didn't have to keep finning all the time".

They may have been overweighted (carrying more lead than is needed for safety stop with near empty tank) or they may have been properly weighted, but just very negatively buoyant because they hadn't put air into the BCD to compensate for wetsuit compression and the 6 pounds of air that they started off with. In either case, both their anxiety level and their air consumption rates went down when they made a conscous effort to maintain neutral buoyancy.

For those divers, at least, the base problem causing high SAC was not overweighting (as in carrying too much lead) but was being negatively buoyant.

Charlie Allen

 

[Codyjp]

They found out from local fishermen, that sharks hate the "scent" of decaying shark meat. So much so, that they pretty much fled from the general area of it. In the lab, they "extracted" essence of rotted shark meat, and tried it out on what looked like (I didnt get a good look, but something like small whitetips or reef sharks) ... when that stuff started spreading in the water, they took off! Literally. I can only imagine what it smelled like though.

-----

Mike.

thanks mike, so much for my bright idea. ugh. so now i just need to find a decaying shark fin and strap it onto my tank. heheehe. that would work well unless i was snorkling on the surface!

 

[rockjock3]

wouldn't it be more like me smelling a kangaroo BBQ as opposed to rubber tires? you make a valid point though. I once cut my finger diving and had a funny feeling the rest of the dive.

I have always wondered if it would be possible to creat a shark mace (pepper oil or something else undesireable...) I could market it to surfers because divers are too smart!

Yes, I thought about using some other kind of animal cooking, but I don't know what they smell like cooking and they might smell appealing to somebody else. Like if you said smelling somebody cooking snake "I" would think food. I just tried to use something that would not smell like even a possible food to somebody.

They already have. If you watched this years shark week then Dirty Jobs, jobs that bite showed it.

There is a marine biologist who found fishermen that drug a dead shark carcass behind their boats to deter sharks from coming around. He did some studies and found that when you let a shark carcass decay that there is a chemical that is formed that actually tells other sharks to avoid the area. He did an experiment on the show where he and Mike Rowe actually got in the water and chummed until there were about 60-100 sharks swimming all around and frenzied around them. They then released a "grenade" (about the size of a can of air freshener) filled with the chemical they extracted earlier in the day from a decaying shark. On the video you were watching underwater all the sharks turned and shot away like they were shot out of a gun and within about 10 seconds there were no sharks withing visual range in any direction. This was 100+ viz, not some murk.

The initial thing he wants to do is is try to get this into the hands of beach lifeguards. He already has designed a gun, similar to a paint-ball gun with a larger barrel. You fill the guns tank from an air compressor or tank and simply drop in a grenade, aim and shoot. It will lob the grenade up to about 250 yards (Mike was shooting them at his crew on a boat just offshore) and the grenade activates when it contacts the water. This could be used to clear sharks out of the area if there is an attack to ensure the safety of the swimmers trying to get out of the water and make it safer for the rescuers to get out to the victim. It was a really cool segment to watch.

 

[Walter]

Bottom line, I think your "do nothing" is at least as far off base as the "instant frenzy" fallacy.
Rick

Isn't it wonderful to live in a world with so many things left to learn? Some even suggest sharks might be attracted not only to human blood, but to human urine and sweat as well.

 

[Daner]

Isn't it wonderful to live in a world with so many things left to learn? Some even suggest sharks might be attracted not only to human blood, but to human urine and sweat as well.

Well does that mean peeing in my wetsuit makes me shark bait? Wait a minute, if they smell my human urine but look at me and think I am a seal, wouldn't they just get confused and swim away. There's a shark repellant for you. Now let me just add that to Wikipedea and it instantly becomes fact!

 

[Walter]

Well does that mean peeing in my wetsuit makes me shark bait?

Possibly, I don't know. I'm trying to remember if I took a leak on the dive when those bulls wanted to eat us..............

 

[Hank49]

Possibly, I don't know. I'm trying to remember if I took a leak on the dive when those bulls wanted to eat us..............

If I was getting circled by some big bulls, a leak might not be the only thing I'd take....

 

[Walter]

I meant before they got aggressive. Afterwards, there wasn't time to take a leak or anything else.

 

[rockjock3]

I'm sure the crew of the Indianapolis will be glad to find out it wasn't their blood that got 'em eaten.
Now I've personally witnessed sharks showing up to check out bloody pork and bloody beef, even caught a few over the years using both. Haven't tried human yet, but suspect they'd check that out too.
While other-than-fish blood may not indicate the presence of the usual fare, some sharks do like mammal, and all the big bitey ones are pretty egalitarian in their flesh selections, if it's an easy target. Bottom line, I think your "do nothing" is at least as far off base as the "instant frenzy" fallacy.
Rick

People (civilian and military alike) have been attacked and/or eaten while stranded at sea. Not all of them have been bleeding. If you know anything about sharks you will know that they are opportunistic feeders. If they are swimming around and smell something (most anything, not just human blood) in the water then yes, they will probably investigate it, just like all those swimmers and surfers that get attacked every year (most of them were not bleeding) it was the sound that attracted the shark and sometimes a chance meeting. If you act like bait then you might become bait. Also, if you are drifting at sea and maybe there aren't many fish around then guess what, when that shark swims by to investigate and you pose no real threat to him, you might just get nibbled on.

I never said that if you slice your arm you just just swim around and have fun. Heck, If I cut myself to any significance (blood flowing, not just a needle stick) and am on dry land I will discontinue what I am doing and clean and dress that wound not because I might attract bears or lions but becasue that is what common sense would dictate.

The part of the myth that bothers me is that people throw that out there like if you are bleeding in the water you should basically kiss yourself off because sharks are coming and they are going to get you. Sharks are not stupid mindless feeding machines. There are specific things you can do that greatly reduce your risk of being attacked by a shark and there are things that if you do them can result in an attack. There are countless more peaceful encounters between humans and sharks every year than there are attacks. Heck approx 200 attacks a year and I myself have been within 50 feet of (counting in my log) 25-30 sharks this year including White-tips, a Scalloped Hammerhead and a Galapogos, while diving, without any of them so much as making an aggressive move towards me. I know many people out there have seen many more that I have.

Yes you can say that human blood attracts sharks, but you can also say splashing in the water attracts shark, dropping a coke in the water might attract sharks, or simply giant striding into the water might attact sharks. Safe move is just don't get in the water at all. Don't just pick out one thing and use it like the holy grail.

How about this.

You want to dive and sharks are in the water (SW and some FW) and could pose a threat to you so educate yourself on sharks and how to not make them interested in you as a food source.

Telling somebody blanketly that human blood attracts sharks translates in a persons head to sharks want to eat humans and just feeds the myth that they are mindless eating machines and to be feared.

That is just my 2 cents.