Upright or Verticals: a common term for tail fins, which usually comprise upright trusses covered by sleeves or fairings often support a horizontal stabilizer.

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Horizontal Stabilizer: loosely called the "wing" the airfoil-shaped surface mounted horizontally above the transom and usually adjustable for trimming. 

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Wing: an aerodynamic surface that can generate lift;

while the term is informally applied to the horizontal stabilizer,

the most important wing on a modern hydroplane is the "ram wing".