The curse of the devils fruit never really bothered Luffy all that much. It was fun and well worth being a rubber man to stretch and have that extra strength to protect his nakama and go after his dream.
Besides he trusted his nakama to save him from drowning and more often than not it would be Sanji holding his exhausted body to his chest as he kicked up to the surface.
Not really so much a curse at all when he thought about it like that.
Therefore it is easy to forget as he is running toward the water and it isn't until he realizes he isn't making any progress that he sees Zoro pushing him back while screaming in his ear.
"Don't go there yourself idiot! I'll go get him! Wait!"
His mind is screaming in anger and confusion at Zoro for stopping him…Sanji has been pulled down by those Flying fish and it is his job to save his blond cook for once….clutch him to HIS chest and be there when he tastes oxygen again. It's his job to protect him…and Zoro is keeping him from jumping in for some stupid reason and time is slipping away because those fish looked fast!
His first mate gives him a serious look and Luffy realizes why Zoro is keeping him from diving after his cook. HIS cook. SANJI.
The curse. Luffy would sink.
For a moment he wonders if maybe he'll sink faster than the fish are swimming and could free Sanji on the way down.
It is already too late to risk it he realizes and he is so close to panicking right now he isn't quite sure what to do.
Sanjis ugly look-a-like is laughing about how the next time they see him he'll be a corpse and it feels like he is mocking the strawhat captain for not being able to simply dive into the water and pull out his lover that had saved him so many times.
Then Hatchi is volunteering to swim after them, then Camie….and Luffy just doesn't care who goes just as someone does right now. He's grateful, but can't show it till this pain in his chest stops.
Someone please save him! Please!
He is feeling what it truly means to bare the curse now…
Someone please save him, because damn it, he can't.