Have your hot tub get a job. Then, it will be self-supporting. (I couldn't resist.)
It depends on the weight of the hot tub. Obviously, w/o knowing how much the combined weight is of the tub, the water (at full level), and the (MAX number of people x 250lbs each), where do you begin? Talk to the folks that sold you the hot tub and ask them for Load Requirements. Then, hire someone who knows what they're doing!
If you don't have this job done right, you'll have a sunken hot tub. There are some things that are best left to a pro. IMO, this is one of them. And get a Pro that installs Hot Tubs. (Maybe you can get a reference from someone else that had their hot tub installed on a deck, like a neighbor. Or, ask the hot tub Retailer for references.)