The pattern of dermatoses among underwater workers is undocumented and, hence, worth studying. The objective of the study was to document the pattern of dermatoses among underwater workers in a tropical seaside area.A population-based cross-sectional study of 1 year from April 2015 among people regularly involved in underwater occupation, especially the collection of mollusks.Among 62 participants analyzed, the commonly noted dermatoses were scars of previous injuries, sea urchin prick reaction, onychomycosis, tinea versicolor, dermatophytosis, warts, and intertrigo. These workers stabilize their position under water by fixing elbows and knees to rocks, where they get accidentally pricked by sea urchins attached to the rocks. Hands also get pricked by sea urchins while trying to pluck mollusks from rocks, thus leading to the predominance of lesions in elbows, knees, and hands.Documenting the pattern of dermatological diseases in any group of underwater workers has not been done previously. Along with doing that, the study also brought to light the existence of a rare disease, sea urchin prick reaction, in notable proportions among an underprivileged group. This study also detected a previously unrecorded clinical finding of a peculiar distribution pattern of lesions over the body in patients with sea urchin prick reaction. The evidence toward possible commensalism between the two species of organisms noted in this study extends its scope beyond the realms of dermatology and opens new areas for research in other branches of science also.