During late April through June, a stinging organism called agua mala or sea lice is prevalent in these waters. These are tiny microscopic jellyfish eggs. An itching hive results within four or five hours after it brushes against you. Always shower immediately after coming out of the ocean. Be sure to rinse under your bathing suit and apply water vigorously to your belly button and all hairy areas such as underarms and pubic hair. If you do get these itchy swellings, which look like a rash rather than mosquito bites, there are a couple of remedies: Logoderm, a cortisone-based creme available in any local drugstore, applied twice daily is a big help. Soyaloid polvo, a poultice applied twice daily will also relieve the itching. Plain white vinegar also helps, especially if sponged on immediately after coming out of the water.