Can't find it in any dictionary.

I am sorry, in what context ? Since people who go out into a boat and use it on the water, may say it. If you are looking for it, in another meaning, you are not clear?

So if I'm going on the water with the boat to "ride" with it, I may use said expression?

To Go Boating is quite an English expression normally used in Oxford and Cambridge or in the 20's

If you look up "boat" in the dictionary you'll find it can be an intransitive verb, as in "I like to boat on the Thames." The phrase "to go boating" is an alternative - "I like to go boating on the Thames" - similar to how you might use "I like to shop in London" versus "I like to go shopping in London."