Dad! Look at muscular mariner!
I believe the answer is:
pop-eye
'muscular mariner' is the definition.
I know nothing about this answer so I can't judge whether this works.
'dad look' is the wordplay.
'dad' becomes 'pop' ('pop' can be a synonym of 'dad').
'look' becomes 'eye' (eyeing is a kind of looking).
'pop'+'eye'='POP-EYE'
'at' is the link.
Can you help me to learn more?
(Other definitions for pop-eye that I've seen before include "Spinach-eating cartoon character" , "'The sailor man'" , "Spinach and Olive Oyl lover" , "Cartoon sailor addicted to spinach" , "Cartoon sailor who loves Olive Oyl" .)