web; webbing
Refers to the skin membrane between fingers or toes of aquatic animals, or sometimes humans.
Frogs have webbing on their feet.
A duck's webbed feet help it swim.
paddle; paddle blade
Refers to the flat blade of a paddle or oar, or the paddle itself. Less common than the webbing sense.
The paddle blade of the canoe broke.
Standard modern spelling using kana for the second part.
Kanji spelling using 掻く; still seen but less common than 水かき.
Search-only form using the kyūjitai 搔.
Single kanji for webbing; rare and mainly used in technical or zoological contexts.
Compound of 水 (mizu, 'water') and 掻き (kaki, 'scratching' or 'paddling'), from 掻く (kaku). The meaning 'web' likely comes from the resemblance to a membrane used for paddling in water.