Foot worn aquatic fin

Aquatic activity fin comprising a foot support portion configured for fixing to a person’s foot, and a fin portion extending from the foot support portion substantially along a base plane (P), the fin portion comprising a support frame, a plurality of hydrofoil blades mounted pivotally to the support frame via pivot couplings, and a mechanism for limiting the maximum blade pivot angle β of each hydrofoil blade, the mechanism for limiting the maximum blade pivot angle comprising bidirectional angle stop configured to allow pivoting of the hydrofoil blade from the a thrust position where a trailing edge of the hydrofoil blade is above said base plane (P), to a return position where the trailing edge is below said base plane (P) characterized in that the bidirectional angle stops are configured to stop the hydrofoil blade in the thrust position such that an angle (γ) of a chord line (C) of the hydrofoil blade with respect to the base plane (P) is in a range of 3 to 30 degrees, and in that the bidirectional angle stops are configured to stop the hydrofoil blade in the return position such that an angle of the chord line (C) of the hydrofoil blade with respect to the base plane P is in a range of 70 to 90 degrees .