Joe Johnson

Yes you can see 2.6 NM to the horizon if you're looking for a stick floating flat in the ocean. But that is largely irrelevant as no one has ever looked for that. If conversely, your feet are 3' above the water (typical sailboat deck) and you're looking for a 60' mast or building or hill, you can see 11.4 NM or very close to August and the other responses you've had. So they had the relevant answer to the typical situation and Andy had the technically precise, irrelevant answer.