I would like to jump in as someone who was once a career English teacher and talk about the fact that there has been much argument about of definitions of key terms in this thread.
In an American football game yesterday, the announcer said that a defensive player had tied an all-time record with his interception return. I will bet that no one in the listening audience shouted out, "No! He didn't set a record! A record is a vinyl disc that will reproduce a sound!" That is because he overwhelming majority of people understand that when we use words, the definitions depend upon the context. A word correctly used in one context would be incorrect in even a slightly different context.
Here are two examples:
Recreational: This word has many different meanings in many different contexts. If you do a google search for the phrase "recreational diving," you will find many of sources explaining what that means. Most will show that it can mean different things in different contexts. I certainly did not do a statistical analysis of the results when I did the search, but my wild guess is that more than 90% of the time, people who use the phrase "recreational diving" are contrasting with a common definition for technical diving and are referring to diving above a 40 meter depth with no decompression obligations and no hard overhead environments. Some people will use the term differently in different contexts, but that does not mean everyone else is wrong.
Safe: The word "safe" is used within the context of the activity. If you get technical about it, nothing is 100% safe. Whatever the activity, there is a range of behaviors that is considered to be within the safe zone. If you are standing at a street corner and a light signal tells you it is safe to cross the street, you can probably cross the street safely 99.9% of the time. On the other hand, when I was in Paris last year, I started to cross a street at just such a time and almost got hit by a car making a right turn at the highest possible speed, a violation of the law. A Parisian explained to me that in Paris, that law is routinely disobeyed, so in the context of Paris, one has to add an extra step in the process of judging safety. The same is true for diving. What constitutes a safe dive depends a generally accepted range of behaviors with the context of the dive.