Charles Ellicott Commentary 2 Chronicles 9:21

"For the king had ships that went to Tarshish with the servants of Huram; once every three years came the ships of Tarshish, bringing gold, and silver, ivory, and apes, and peacocks." — 2 Chronicles 9:21 (ASV)

For the king’s ships went to Tarshish. — 1 Kings 10:22, “For the king had a Tarshish fleet on the sea, with the fleet of Hiram.” It is generally assumed that the words of the chronicler are an erroneous paraphrase of the expression, “Tarshish fleet,” i.e., a fleet of ships fitted for long voyages. (Compare to Isaiah 2:16.)

The identity of the present fleet with that mentioned above in 2 Chronicles 9:10 is not evident. Solomon may have had a fleet in the Mediterranean (“the sea” of 1 Kings 10:22) trading westward, as well as in the Red Sea, trading south and east.

Some have identified Tarshish with Cape Tarsis in the Persian Gulf. (See Note on 2 Chronicles 20:36.)