I'm familiar with some serious discussions about preposition particularly when it comes to kind of "at" vs "in" involved. I know that "at" suggests a point in space and "in" requires being confined, enclosed in the area. Taking all the information we know into consideration, where does one imply to be exactly by saying "I'm at sea" (apart from its idiomatic meaning for sure).
Is he far away from the coast on the water in/on the boat or any vessel? Or is he on the coast anywhere near the sea? Or both are possible?
After learning the fact that "being at sea" and "being at the sea" are not the same thing, I have to include the following question in my post ; - how come the article "the" make such a difference like "being close to the sea(seaside)" and "being on an open sea/ocean" ? (please mention it in your answers)