Aqua bag

Filled with water and air, an aqua bag is a soft, handled training bag that changes shape as you move it. The water shifts inside, so the load can feel lively and less predictable than a solid dumbbell. You can grip its handles, hug it to your chest or support it across your shoulders, depending on the design.

You can use it for strength, balance and whole-body movement, lifting it from the floor, carrying it, pressing it overhead or moving it around your body. Because the water continues to shift, you have to stay controlled as you squat, step, bend or turn. Changing the fill level alters both the load and how freely the water moves.

It can suit you if you want one adaptable tool and enjoy movements that ask for steady attention. Filling and emptying it makes the load easy to scale, although water is heavy and a partly filled bag can move suddenly, so start gently and check the closure. You need clear floor space; a sturdy backpack with water bottles offers a simpler alternative.