There has been some discussion of whether towing a tube or wakeboard behind the Spark is possible (which it is), what the legality of that is, and tips on how to do it best. I did a little research and here is what I found.
So my first order of business was to figure out if it was even possible for the Spark to tow a tube or wakeboard. A simple search of YouTube showed some examples of people doing this successfully. Here are the videos to prove that the Spark is capable.
So it's possible, but there are other things that you need to think about before you just start towing your friends around. Different jurisdictions have different laws regarding the legality of towing someone with a PWC. If there are laws in your area, the law usually says that you must have a spotter, or a rear view mirror. The law also states that you must have a seat for each person with you. That means that if you are taking along a spotter, you will need to have the 3up Spark so that you have a spot for the driver, the spotter and the person being towed. Again though, look up the laws for your area specifically.
Finally, here are some accessories that might be a good idea to pick up if you plan on towing your friends around. One accessory that is necessary is some type of protector on your tow rope to prevent it from getting tangled in the jet engine. A step will make it easier for people to get back out of the order once they are finished being towed behind your Spark. A ski eye or U-bolt helps out with the tow rope placement, and a board rack makes it easier to store your wakeboard when you aren't riding it.