What is the likely diagnosis for a patient with an erythematous ear canal and pain on manipulation of the auricle after swimming?

The situation described points towards external otitis, often referred to as swimmer's ear. This condition typically manifests as inflammation of the external auditory canal, which can be triggered by water exposure, such as swimming. The erythematous appearance of the ear canal indicates an inflammatory response, while pain upon manipulation of the auricle is a classic sign of external otitis.

In this scenario, the patient's pain and the redness of the ear canal are key indicators that suggest an external cause rather than an internal infection. Acute otitis media typically involves the middle ear and does not usually present with pain on auricle manipulation. Chronic otitis media represents a long-standing middle ear infection that wouldn’t be characterized by an erythematous ear canal or increased pain from the ear's outer structure. Temporomandibular joint syndrome involves pain related to the jaw movement rather than the ear canal itself.

Thus, the combination of symptoms, including the specific pain response and the erythematous condition of the ear canal following swimming, supports the diagnosis of external otitis as the most likely explanation for the patient's presentation.