I scream, you scream, we all scream for ice cream! Well sharks all scream for people if that is the case. There has always been a well known fallacy that when there is a rise in ice cream sales, that there is a rise in shark attacks. So this is basically stating that since there is a positive correlation between these two things, that they must cause each other? Psychology tells us no. This is one of the most well known cases used to explain the second scientific thinking principle: correlation ISN'T causation.
The correlation-causation fallacy basically states "error of assuming that because one thing is associated with another, it must cause the other". This ties in perfectly with what has been given to us here. Are ice cream sales really the reason of high shark attacks? There are two variables in this scenario but there are so many other variables that could be lingering behind all of this. For example, when do people crave ice cream the most? Usually over the summer when it's hot. What does hot weather bring? Days out on the beach and in lakes, or in this case, oceans. Many swimmers out in the ocean is a buffet for sharks, probably being the main reason for the many shark attacks. This is such a more reasonable alternative to "high sales in ice cream is the reason there are many shark attacks". There are many other explanations that can be used still. However it just needs to be known that just because two things might be related and correlated, doesn't necessarily mean that they are the reason one another is happening.