The sentence that you quote is the first line of the song "Yellow Submarine", sung by the Beatles. So I have to believe that "sail to sea" is a fixed expression, although I haven't heard it in. Setting sail is fairly specifically a beginning process.

Understanding the Context

There is less implication that you will get there successfully, so 'for' (intended destination) is more appropriate. You sail to a place ('to' for. I am going to sail my boat. This irrespective of the type of boat.

Key Insights

Obviously a sailing boat is sailed, but motorboats and even liners are also sailed particularly if the steersman is not specified. For. You're right, the common phrase is 'set sail'. You can use 'set' with -ing verbs e.g. I saw an advert for Bali and that set me thinking about holidays.

Final Thoughts

So it may have been used deliberately in the. I understand your point, but just because you dont like it, that doesnt mean the definite article is wrong. Plenty of reputable sources do use one when referring to ships. Charles Darwin and his. That depends on the circumstances. Suppose a rich uncle dies, leaving you a billion pounds in his will.

Suppose the validity of the will is now challenged in court. Are you a billionaire? That. canot is a generic term for a small boat : paddle , rows, sail , small outboard engine.