Sail to discover those magic islands
Sail - here it means, travel by ship on or across (a sea).
How grammatical the use of the word "sail" here? (even if we think little poetically)
An advertisement might say,
"Sail away and discover those magical islands."
Is that what you want? Your usage of "Sail to" in your example is troubling.
[FWIW I've said this before elsewhere, sorry - but as a learner you will do well to stick to what you hear said in its specific context].