Can Water Play Calm Babies? Here’s How, According to Science

If your baby lights up during bath time, there's science behind those smiles. Research shows that water activities can actually lower stress hormones in infants while also giving them a full sensory workout.

The Swimming Study That Surprised Researchers

Researchers at the University of Minnesota wanted to know if completely new experiences would stress babies out. They brought 48 babies (ages 6-13 months) to infant swimming classes and measured their stress hormones before and after.

Swimming was the perfect test because it was totally new. These babies had never been in a pool before. New sounds echoing off the walls, the smell of chlorine, different water temperature, and the sensation of floating. The researchers figured all this novelty might trigger a stress response.

It didn't.

What They Found: Happy Babies, Lower Stress

The results were striking:

Babies were happy 95% of the time. They smiled, cooed, splashed, and kicked. They were actively engaged and clearly enjoying themselves.

Cortisol levels dropped. Here's the key finding: after swimming, babies' cortisol levels (the stress hormone) were lower than when measured before swimming.  Swimming wasn't just non-stressful, it was physiologically calming.

Even cautious babies relaxed. Some babies were hesitant at first, especially those described by parents as generally fearful. These babies clung a little more tightly to mom and took their time warming up. But, even these babies weren't stressed - their cortisol didn't spike. By the second swim session, most cautious babies were comfortable and engaged.

Why Water Works: The Sensory Science

Water is a sensory experience unlike anything else babies encounter. In the pool or bath, babies feel the wetness against their skin, hear splashes and echoes, see ripples and waves, and experience their body moving in a new way. It's sensory input on every front.

The researchers found several reasons why this translates to calm:

Movement freedom. On land, gravity limits how babies can move. In water, those chunky little legs can kick freely and smoothly, arms can wave easily, and every splash creates an immediate, visible effect. Babies in the study were "vigorously exploring", testing what happens when they kick, watching water droplets fly, feeling the resistance and flow.

Physical closeness matters. Mothers held their babies close throughout the sessions, keeping their heads above water. The physical security of being held by a caregiver appeared essential to the positive experience.

Positive emotions drive the response. This was a major conclusion: emotions matter more than novelty. Because babies experienced swimming with joy rather than fear, their bodies responded with relaxation. The newness didn't cause stress when the experience itself was positive.

Using Water to Soothe Your Baby

Based on the research, here’s how you can use time in the water to help your baby:

Start where your baby's comfortable. Cautious babies in the study needed time. Start with a shallow sink bath or brief sessions before moving to bigger water experiences.

Stay close. Hold your baby securely, keep them near your body. Your physical presence matters.

Get the temperature right. The study used water around 85°F, which is comfortably warm. Too cold or too hot changes the experience.

Let them explore. Splashing, kicking, and watching the water move seemed to contribute to the calming effects and kept babies actively engaged.

Be patient. Hesitant babies often warmed up by the second session. Initial caution doesn't mean your baby won't eventually love water!

No Pool or Swim Lesson Access? Try Otteroo in a Bath Tub! 

Otteroo lets babies explore in the water without the usual constraints of gravity. This freedom can help babies experience new sensory input as they move through water.

Tips for a Positive Otteroo Experience

• Start with short sessions and gradually increase time as your baby gets comfortable.

• Keep the water bath water warm (around 98°F is ideal).

• Talk, sing, and make eye contact to reassure your baby.

• Get in the tub with them if you like!

• If using Otteroo in the pool, there should be an adult in the pool next to the baby at all times!

• Watch for your baby’s cues.If they seem happy and curious, let them explore; if they seem tired or fussy, end the session.

Safety First
As with any water activity, supervision is absolutely essential. Always stay close enough to lift your baby out at any moment if needed and never leave your baby unattended, even for a second. If your baby seems uncomfortable or distressed, remove the Otteroo and comfort them in your arms.

The Bottom Line

When babies have positive water experiences, their bodies actually relax. Stress hormones go down, engagement goes up.

That's why bath time can transform a fussy baby. It's not just a distraction. Water provides unique sensory input, movement freedom, and when done right, genuine physiological calm.

Whether you're filling the bathtub or visiting a pool, time in the water can be a real tool for soothing and exploration, backed by actual science.

References:

Hertsgaard, L., Gunnar, M., Larson, M., Brodersen, L., & Lehman, H. (1992). First Time Experiences in Infancy: When They Appear To Be Pleasant, Do They Activate the Adrenocortical Stress Response? Developmental Psychobiology, 25(5), 319-333.