Water creature had to hide in locks (7)

I believe the answer is:
manatee
'water creature' is the definition.
The definition and answer can be both animals as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'had to hide in locks' is the wordplay.
'had' becomes 'ate' (e.g. I had an ice cream).
'to hide in' indicates putting letters inside.
'locks' becomes 'mane' (both can mean hair).
'ate' put within 'mane' is 'MANATEE'.
Can you help me to learn more?
(Other definitions for manatee that I've seen before include "rare sea mammal" , "To find sea cow" , "Sea cow - emanate (anag)" , "A neat me (anag) - large aquatic mammal" , "sea creature appears" .)
