Relationship between Sanji and Nami
One Piece: 5 Reasons Why Nami Should Be With Luffy (& 5 She Should Be With Sanji)
Sanji and Nami
So while you classify Sanji as "just a cook" know that the cook is often in charge of protecting your favorite girl.
Being as dedicated as he is, Sanji's more than willing to risk his life to help Nami.