Panda, the sand in Hawaii is about 12-18" deep and nothing but powder essentially. It isn't like the sand beaches in WA/OR or even on the outer banks. I watched a friend with 15.5" wide tires sink his F-150 on this sand. Granted, it didn't help that his truck was only a 2wd.
But, like I mentioned, I didn't get stuck, I simply found that the truck needed tons more power to make it through and also required 4hi.
When I lived in Hawaii... the beaches I went to were easy to walk on. Realitively firm sand now I admit I never went to a beach that you drive on. The sand in the outer banks is deep.... at least in Avon, ocean side that is. It takes a lot of effort to walk through. I actually drag bottom frequently with the stock suspension. I have seen plenty of 4wd's get stuck there. Thats actually part of the fun.. lol. One huge bronco with lift kit monster tires ect... came blazing in one day and made it appr 300 ft before he got stuck. It turns out it was either 2wd or his 4wd was not working as he just started sinking his rear wheels in. Just saying I don't think you can get any deeper sand. Its a blast to drive in. Momentum is your friend! I will try and get some good photos this year.
Just dont go on a windy day as it will sandblast your truck!!