Dilemma faced at sea, perhaps, but they'll succeed or fail through their own effort (4,2,4)
I believe the answer is:
sink or swim
'dilemma faced at sea perhaps but they'll succeed' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'or fail through their own effort' is the wordplay.
I cannot quite understand how this works, but
'or' is within the answer.
'through' could be 'in' and 'in' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sink or swim that I've seen before include "Survive (or not) by one's own efforts" , "To succeed or fail (the only options!)" , "Cope (or not) unaided" , "Do/die strategy" .)