River fish, first to dive to the bottom, moved quickly (5)

I believe the answer is:
raced
'moved quickly' is the definition.
(I've seen this in another clue)
'river fish first to dive to the bottom' is the wordplay.
'river fish' becomes 'rac' (I am not sure about this - if you are sure you should believe this answer much more).
'first to' indicates taking the first letters.
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'bottom' suggests the final letters.
The first letter of 'dive' is 'd'.
The last letter of 'the' is 'e'.
'd' after 'e' is 'ed'.
'rac'+'ed'='RACED'
Can you help me to learn more?
(Other definitions for raced that I've seen before include "went at speed" , "Hurried" , "Cedar (anag)" , "Took part in speed contest" , "bolted" .)
