In humans, a vacation at the seaside frequently ends with sunburn, especially for those with fair skin. A study conducted at the Gulf of California showed that exposure to UV radiation can be just as harmful to whales: three different species, fin, sperm and blue whales, were observed and skin biopsies were taken. They differ in their pigmentation as well as their exposure to sunlight, owing to their different surfacing behaviors. During the period of observation (January 2007 — June 2009), it was found that whales with light skin tones had more lesions than those with darker color. As blue whales spend most of their time in polar waters, their skin produces less melanin. Therefore, it is not as well protected as the skin of fin whales, the darkest of the three species. Although sperm whales have relatively high melanin levels, their skin still suffered a lot of damage, due to the fact that they spend more time at the surface for breathing and socialization.
Sources: Martinez-Levasseur, L. et al., “Whales Use Distinct Strategies to Counteract Solar Ultraviolet Radiation”, Sci Rep, vol. 3, (2013).