Prepositions – Do You Windsurf and Kitesurf ‘on’ the Sea or ‘in’ the Sea?

We use the word "to" to indicate a direction or progress in a direction. We say "just to your left" or "far to the north", to indicate places in those directions. "Just out to sea", then, means a little way in that direction from the water's edge.

I think the preposition is necessary. The analogy with case in point is not quite apt as follows: "In which city" can be replaced with "Where", hence "Where are you located?" is correct but "In where are you located?" and "Where are you located in?" aren't. Similarly, "What time is the meeting?" or "When is the meeting?" is correct, but not "At when is the meeting?"