(From the link...)
"Kappa, arguably Japan’s most well-known creature of legend, are mischievous river imps notorious for luring people — particularly children — into the water to drown and eat them. They smell like fish, enjoy cucumbers and sumo, and are said to be very courteous despite their malicious tendencies.
Although kappa are typically about the size of a child and greenish in color, they can vary widely in appearance. They frequently have a turtle-like shell and scaly skin, but sometimes their skin is moist and slick, or coated in fur. Most walk upright on their hind legs, but they are occasionally seen on all fours. Regardless of body type, the top of the kappa’s head usually features a bowl-shaped depression containing water. The water inside this bowl is the source of the kappa’s power. "
Lots more info on the website.