Issue 3: Why Weight Behaves Differently in Water
Issue 3: Why Weight Behaves Differently in Water
A 25-lb object is still 25 lb, but the effort to move it changes depending on whether it is under the water, above it, or passing through the surface. That is one of the most interesting things about aquatic strength training.
Research Spotlight
A 2026 meta-analysis in the Journal of Strength and Conditioning Research pooled 13 controlled studies of 392 competitive athletes. Aquatic training significantly improved explosive power, speed and agility, and had a modest benefit for recovery and fatigue. Here's the surprising part: the gains in strength and balance were not statistically significant.1
That matters. Most water training in these studies built power and speed, not maximal strength. For strength, the research points to the same thing as Issue 1: you need a load you can progress. These studies used a range of aquatic methods and did not test AquaBLAST.
Water Science
- Underwater: buoyancy supports the load and drag resists motion.
- Through the surface: buoyancy decreases and gravity increases, so the load gets heavier as you lift.
- Reversing: the load lightens as it re-enters the water.
Mix air with the water and buoyancy becomes another variable. You can push a more buoyant bag down, sweep it sideways against drag, or carry it through the surface.
Inventor's Notebook
I didn't fully appreciate this when I first built AquaBLAST. I had made a way to add progressive weight in the pool, but the same bag could also move above and below the waterline and change behavior with different water-and-air mixes. It isn't one fixed resistance: weight, buoyancy, drag, speed, depth and direction are all adjustable.
Myth vs. Fact
Myth: A pool weight should feel the same through the whole rep.
Fact: As a load moves between water and air, buoyancy's contribution changes continuously. That's what makes aquatic loading distinctive.
Try It Yourself
With a light-to-moderate fill, start with AquaBLAST submerged and do a slow two-handed lift until part of the bag is above the surface. Note where it feels heaviest. That is the transition point. Lower it slowly and feel the load shift back. Keep the lift at or below shoulder height until you know how your fill level feels.
Safety: Work in waist- to chest-deep water where you can stand firmly, near the pool wall or a rail. Keep your head above water, move with control, and stop if you feel pain or dizziness. If you have a medical condition, or you are recovering from injury or surgery, follow your healthcare or rehabilitation professional's guidance.
Where AquaBLAST Fits
AquaBLAST is designed for the pool. You choose the load by how much water you add: a few gallons for lighter technique work, up to a full bag of about 40–45 lb (20L) or 50–55 lb (25L). Out of the pool, it is suited to light land training with up to about 2 gallons of water (roughly 16 lb of water plus the bag). Save slams and throws for the pool.
Shop AquaBLAST 20L V2 → · Shop AquaBLAST 25L V2 → · 20L V1 (while supplies last) · Add the Suction Tether
More exercises: Aquatic Fitness Guide · All issues: Strength in Water® Blog
Blast Away!
— Rob Magrino, inventor of AquaBLAST
Research Notes
These studies looked at aquatic exercise in general. None of them tested AquaBLAST.
- Zheng S, Wang S, Cao Q, Li H. The impact of aquatic training on athletic performance and physical recovery in competitive athletes: a meta-analysis. J Strength Cond Res. 2026;40(6):723–737. doi:10.1519/JSC.0000000000005469
