Though the series premiered in 1967, it can clearly be seen by the Roman numerals at the end of the episodes that they were created in 1965.
When actor Frank Converse is climbing up the ravine from the beach to confront the sniper, he is nearly struck by a dust hit (special effect that simulates a bullet striking a solid object). You can see him flinch when the dust hit strikes a rock very close to him, and you can see the dust that stuck to his face later in the shot.