In a Hot Tub - you sweat from the increased temperature not from burning fat. So any weight loss is due to the weight of the water you loose.
Be sure to set the temperature of your hot tub to not exceed 105 degrees (F).
This being stated, we recommend using aqua aerobics in a pool - as a low impact form of exercise.
Aqua aerobics in a pool has of late become a popular way to try to lose weight. There are some add-ons that allow you do do aerobics in your hot tubs.
Check with All Brevard to see what they recommend.