ἐνίοτε οἱ οἰκέται εἰς τὴν θάλασσαν ἐλαύνουσιν αὐτούς → sometimes the slaves ride them into the sea
See tax.
liable to taxation: P. ὑποτελής, φόρου ὑποτελής, ὑποτελὴς φόρου.