What is the opposite of land?

Answer 1

The opposite of land is typically considered to be water. Land refers to the solid surface of the Earth, while water encompasses the liquid bodies found on the planet. This differentiation is based on the fundamental distinction between terrestrial and aquatic environments in geography and Earth Sciences.

Answer 2

The general opposite of the noun "land" is "sea." These are the two types of surface. Historically the opposite of travel by land was by sea, but this could now apply to travel by "ground" as opposed to by "air."

If you are referring to what an aircraft does, then 'take off' would be a suitable opposite. For sea travel the opposite could be to "set sail."

If you refer to what you do to a fish after hooking it, then the opposite might be 'lose' but it is not so clear.

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It really depends upon which meaning of 'land' you mean and exactly what you mean by 'opposite'. When people refer to the 'opposite' of a word they normally mean its antonym and this would typically only apply to adjectives and adverbs, and certain verbs that have a clear antonym, and to nouns based on them.