How Far Can a Shark Smell Blood in the Ocean?

[Ratman101]

I have read that a shark has great sensitivity to smelling blood from a large distance. In an open, calm sea, just how fast can blood molecules diffuse through sea water for a shark to detect??

 

[BillTre]

In an open, calm sea, just how fast can blood molecules diffuse through sea water for a shark to detect??

I don't know, but probably not a whole lot.
However, the water could also flow and the emitter of blood could also move. Either of these would leave a trail (or plume) for the shark to follow.

 

[DaveC426913]

To put it in perspective, just because, technically, a shark can sense a certain concentration of blood in a volume of water does not mean this actually occurs in a way that allows them to utilize it to it potential.

Take a bucket of water - dilute it in a volume of water the size of |lake Superior - mix well. The shark will detect it - in the bucket. That's really all it means.

It is a measure of the sensitivity of the sharks' senses; it is not a measure of how far away a shark can be and still zero in on blood from miles away - unless circumstances permit it.