There is a huge range of equipment that can increase or decrease the difficulty of aqua fitness exercises.
The high-quality foam is used as the primary form of resistance in items such as aqua dumbbells, round hand buoyancy, aqua gloves. These are lightweight when out of the water but when used underwater increase the difficulty of the simplest of exercises.
Other items such as bone water dumbbells or aquatic weights are heavier out of the water so increase the difficulty even more when used in water, providing both added weight and water resistance.
Buoyancy belts are a great way of keeping yourself afloat while in deeper water suspending the body at shoulder level in the water. This allows you to move freely underwater increasing the range of exercises you can perform while keeping your head above water so you can breathe naturally.