Learn Russian: Мы любим южное море.

The verb is любить (to love). It must match the subject мы (we). Because любить belongs to the second conjugation group of verbs, its 'we' form takes the -им ending.

Is южное море in the accusative case since it is the object being loved?

Yes! It is the direct object of the sentence, so it is in the accusative case. However, because море is an inanimate neuter noun, its accusative form is identical to its nominative (dictionary) form. The adjective южное follows the exact same rule.

How can I tell that море is a neuter noun?

In Russian, a noun's gender is almost always determined by its last letter. Nouns that end in -о or -е, like море (sea), are neuter.

Why does the adjective южное end in -ое instead of -ый?

Adjectives change their endings to match the gender, number, and case of the noun they describe. Because море is a neuter noun, the dictionary form of the adjective южный (southern) drops its masculine -ый ending and takes the neuter ending -ое.