Are swimmer’s itch and sea bather’s eruption the same thing?

No. Swimmer’s itch, also called clam digger’s itch and bather’s itch, is caused by the penetration of the skin by schistosome cercariae that normally infest birds. When first exposed, the victim will have a prickly eruption within a few minutes of cercarial penetration that rapidly resolves. Repeated exposure with an allergic response leads to larger, longer-lasting, and more pruritic papules that may cause pustules, blisters, and dermatitis. As with creeping eruption, the parasite cannot complete its life cycle because it cannot penetrate the epidermis.

Sea bather’s eruption is caused by contact with larval forms of a marine jellyfish. In contrast to swimmer’s itch, which presents with lesions in exposed areas, sea bather’s eruption typically presents with pruritic macules and papules in areas covered by clothing. It is felt that the clothing holds the larvae close to the skin long enough to cause a small sting.