These toys use water-activated technology: when you drop a fish into water it triggers the water-activation mechanism and the toy comes to life and swims.
The fish swim in multiple directions (up to five directional movements are listed) and are described as able to dive as deep as 6 ft.
Smaller fish typically require 2 LR44 alkaline button cell batteries, while a larger figure in the set lists 3 AAA alkaline batteries.
Review summaries report that the toys provide strong entertainment and engagement for children, praise realistic swimming motion and directional movement, note included items like sand as a fun bonus, and mention mostly positive ease-of-use—one reviewer noted a small screwdriver may be needed for screws.