Try researching similar recreational businesses. If there are any larger companies which happen to be publicly traded, you may find some market information in their reports or reference to where to find it.
You could also look for pulbic records of similar businesses. I expect there is some liscensing involved or maritine records which would indicate how many similar businesses are based in a particular harbor.
There may be a local trade or government tourism organization which could be helpful.
Report Franklin's answer
It doesn't limit to tourism, but I would start there. I'm not sure if you're planning on selling the jet pack or create the attraction. If it's to create the attraction I would definitely research tourism in the area you're planning to operate, specially focused on beaches and hotels off the sort.
Report Victor's answer
Thank you for your response Victor. It will be the attraction, NOT merchandising.