Expandable water toy

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The "Grow A Boyfriend" expandable water toy shown at its original size

Expandable water toys or grow-in-water toys, or grow monsters are novelty items made from a superabsorbent polymer. They are toys that expand after putting them into water for several days. Also, it shrinks with salty water though most shrink simply from air after being removed from water. They are made from polymers that can absorb and retain extremely large amounts of a liquid relative to their own mass.[1]


Grow Monsters come in many different shapes and sizes. Reptiles and dinosaurs are common figures, but there are many others, such as: sharks, squid, seahorses, lobster, insects, humans, and mechas from popular anime are among them. Many of the companies that distribute them are Chinese and Dutch trading companies.[2][3]

Water Balz look like marbles, but expand to the size of a racquetball in water.[4]


The introduction and popularity of these toys has followed the development of superabsorbent polymers. In the early 1970s, the superabsorbent polymer was used commercially for the first time for disposable hygienic products. The first product markets were feminine sanitary napkins and adult incontinence products. The development of superabsorbent technology and performance has been largely led by demands in the disposable hygiene segment. Strides in absorption performance have allowed the development of the ultra-thin baby diaper which uses a fraction of the materials – particularly fluff pulp – that earlier disposable diapers consumed. Over the years, technology has progressed so that there is little if any starch-grafted superabsorbent polymer used in disposable hygienic products. These super absorbents typically are cross-linked acrylic homo-polymers (usually sodium neutralized).

Risks and recalls[edit]

Starting from January 15, 2007 there have been several recalls on these toys. Ireland, Poland, Cyprus, Lithuania, Hungary and the United Kingdom have recalled the Magic Grow Reptile and Dinosaur Eggs Wild World due to a choking risk. They claim the products pose a risk of choking due to the fact that after 72 hours in water, the toys expand more than 500% in three directions, and that the products do not comply with the Toys Directive and the relevant European standard EN 71.[5]

Water Balz and Orbeez have been swallowed and lodged in the guts of children, requiring surgery to remove.[4][6]


  1. ^ Horie, K.; Barón, M.; Fox, R. B.; He, J.; Hess, M.; Kahovec, J.; Kitayama, T.; Kubisa, P.; Maréchal, E. (2004). DEFINITIONS OF TERMS RELATING TO REACTIONS OF POLYMERS AND TO FUNCTIONAL POLYMERIC MATERIALS (PDF) (Report). 4. Berlin: INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY. pp. 889–906. Retrieved 2019-12-25. 3.27 superabsorbent polymer: Polymer that can absorb and retain extremely large amounts of a liquid relative to its own mass.
  2. ^ "Archived copy". Archived from the original on 2009-01-15. Retrieved 2009-03-10.CS1 maint: archived copy as title (link)
  3. ^ "Archived copy". Archived from the original on 2009-02-17. Retrieved 2009-03-10.CS1 maint: archived copy as title (link)
  4. ^ a b O'Connor, Anahad (17 September 2012). "Expanding Ball Toy Poses Hazard to Children and Pets". Well. New York Times. Retrieved 18 November 2012.
  5. ^ "Archived copy". Archived from the original on 2013-01-15. Retrieved 2019-08-14.CS1 maint: archived copy as title (link)
  6. ^ Michelakos, T; Tanaka, M; Patel, MS; Ryan, DP (1 April 2019). "Orbezoar: A Superabsorbent Polymer Causing Small Bowel Obstruction in a Toddler". Journal of Pediatric Gastroenterology and Nutrition. doi:10.1097/MPG.0000000000002357. PMID 30964823.