In favor

There is a higher humidity in coastal areas, which helps keep skin hydrated.
Food richer in fruit and vegetables, increasing hydration. 
Improved hydrolipid by increased sweating.
By using less makeup, let the skin breathe freely.

Counter

Too much sun. The more, worse, wrinkles, dehydration and cause stains.
The air conditioning, high-powered dehydrator.
Insensible water loss through sweating if not offset by extra fluid intake.
The chlorinated water of swimming pools and the salt from seawater.