Yes, it is true that you can take a break by hanging onto a kayak. However, there may not be that many kayaks and there may not be a kayak close by. I wouldn't sign up for an open water race unless I was sure I could complete more than the required distance. Sometimes the courses are longer than they should be and sometimes you may sight poorly and swim a whole lot farther than you need to. I like to be over-prepared for what I may face.

I just learned how to swim last summer and have only done two OW tris. However, I swam in open water a lot last summer and intend to do so again this summer. Knowing that you can do it goes a long way towards relieving race day jitters and will likely increase your enjoyment of the whole day.

I think it's a great idea to see if you can do the entire swim before signing up. If you are not ready yet, there will be many other races later in the year.

Good luck!