Why do bottlenose dolphins have waterproof skin?

Bottlenose dolphins have waterproof skin primarily due to a unique structure and composition of their epidermis, which consists of multiple layers that help reduce water permeability. The outer layer is rich in lipids, creating a barrier that prevents excessive water absorption while allowing for flexibility and movement in their aquatic environment. This adaptation is essential for maintaining their body temperature and protecting them from the marine environment. Additionally, their skin is designed to facilitate streamlined movement, improving their swimming efficiency.