Swim Diaper for a 1 Year Old: Size, Fit and What to Buy

Swim Guide · Swim diapers

By Vivian W · Updated October 2026

A 1-year-old can fit either swim diaper size, so go by weight. Under 24 lb, choose Ocean Pals 6–12 M. From 24 to 33 lb, choose 12–24 M. Near 24 lb, measure the waist and size down if still unsure. A reusable swim diaper suits first-birthday swim lessons. From $23.99.

The first birthday is when many families start swimming in earnest. The AAP says children "can begin swim lessons after their first birthday, depending on readiness." It's also when babies start walking, squatting and climbing out at the pool edge. That puts new demands on the leg openings of a swim diaper.

What size swim diaper for a 1 year old?

Weight at 12–18 months Ocean Pals size Waist Thigh Tip
Under 24 lb 6–12 M 13.4–18.5 in 6.7–10.2 in Check both leg openings sit flat
Around 24 lb Measure first Compare both ranges Compare both ranges Size down if still between sizes
24–33 lb 12–24 M 16.5–19.7 in 8.7–12.2 in Gives walkers room to squat and climb
Over 33 lb Not a fit — — Look for a larger toddler size

Measure the waist at the belly button and the thigh at its widest point, with a soft tape and without squeezing. Weight comes first. Measurements settle a tie. For the full chart, see what size swim diaper does my baby need.

Shop Ocean Pals 6–12 M and 12–24 M

What changes at age one

  • More movement. Crawling and walking pull at leg openings. A pull-on cut with soft neoprene and polyester-spandex openings is made to move with your child.
  • More solids. Once babies eat more family food, the swim diaper's job matters more. The CDC says swim diapers "might hold in some solid feces (poop), they are not leak-proof." Fit is what makes the difference.
  • More swims. Weekly lessons make reusable swim diapers worth it. Rinse after class and reuse all term.

Reusable or disposable for a 1 year old?

Reusable (Ocean Pals) Disposable swim diaper
Best for Weekly lessons, pool membership, holidays One-off swims, backup in the bag
Cost pattern One purchase: $23.99, or $34.99 for 2 A new one every swim
After swimming Rinse, hang to dry Bin it
Holds pee? No No

More detail: reusable vs disposable swim diapers.

Pool-day checklist for a 1 year old

  1. Swim diaper on in the changing area. Check both leg openings sit flat with no gaps.
  2. A swim vest, if your class allows one. Mermaid Dreams fits 6–24 months up to 33 lb and goes over the swim diaper.
  3. The CDC advises checking swim diapers about every 60 minutes and changing them away from the poolside.
  4. Stay in the water with your child, within arm's reach.
  5. After swimming, rinse the swim diaper in fresh water and hang it to dry.

Add the Mermaid Dreams vest, $36.99

Questions parents ask

What size swim diaper for a 1 year old?

Go by weight. Under 24 lb, Ocean Pals 6–12 M. From 24 to 33 lb, 12–24 M. Near 24 lb, compare the waist: 6–12 M fits 13.4–18.5 in, 12–24 M fits 16.5–19.7 in.

What is the best swim diaper for a 1 year old?

One that fits snugly at the waist and legs and still lets a new walker squat and climb. For regular swimming, a reusable neoprene pull-on like Ocean Pals saves buying disposables every time.

Can a 1 year old wear a reusable swim diaper?

Yes. Ocean Pals is sized for 6–24 months, so a 1-year-old fits one of the two sizes depending on weight.

Does a 1 year old need a swim diaper at the pool?

Usually. Pools and swim schools generally ask children who are not potty trained to wear one. Check your pool's rule.

Can a 1 year old wear a swim vest?

Yes, if your class allows it. Mermaid Dreams fits 6–24 months up to 33 lb. It is a swim training aid, not a life jacket, so stay within arm's reach.

Adult supervision within arm's reach, at all times. Paddle Pals vests are swim training aids, not life jackets, and are not USCG approved. Swim diapers provide no buoyancy.

Sources

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