This case report delves into an intriguing presentation of Mycobacterium marinum infection in a patient with spontaneous non-healing ulcers in the hand accompanied by dermal lymphatic nodules in the arm. The patient's history revealed a direct correlation with the onset of symptoms following routine maintenance of a home fish tank, shedding light on the association between aquarium exposure and atypical mycobacterial infections. The clinical manifestation included persistent, non-healing ulcers in the hand, suggesting a potential portal of entry for the mycobacterial pathogen. Additionally, the emergence of dermal lymphatic nodules in the adjacent arm posed an unusual aspect to the presentation, prompting a comprehensive investigation. This case outlines the diagnostic challenges faced, emphasizing the need for a high index of suspicion for mycobacterial infections in patients with unusual dermatologic presentations. The case discussion includes details on microbiological cultures confirming Mycobacterium marinum, and the correlation between the patient's exposure history and the unique clinical findings. The overarching objective of this report is to raise awareness among healthcare professionals regarding the potential cutaneous manifestations of Mycobacterium marinum and to encourage a thorough investigation, especially when linked to activities involving aquatic environments, such as fish tank maintenance. The case underscores the importance of a multidisciplinary approach for accurate diagnosis, appropriate treatment, and prevention of potential complications in similar cases.