SHORT COAT - STRAIGHT COAT - WIRE COAT

The inheritance of long coated PWDs is due to MUTATION envolving different genes. These POLYGENES are inherited independently - and interaction does occur at the phenotype level.

Wavy coat being recessive to straight coat.
Curly coat being recessive to wavy coat.
 

Wavy coated PWD Curly coated PWD
Miss Bella Infanta De Gifford Aslan Infante De Gifford
  

 

  
Black wavy Black curly
 
In the early days, during decades, PWDs were owned almost exclusively by fishermen.
Matings were done mainly at random or according to individual merits - swimming - retrieving.
Brown wavy Brown curly
 
Recently breeders (1970-1990) for grooming 'reasons' embarked in mating, almost exclusively,
curlies x curlies. The result had several health failings not to mention the damage to the genetic pool.
White wavy White curly
 
Now-a-days, due to fashion and marketing demand, breeders are mating wavies to wavies - the result PWD with almost straight hair in their different variations.

SHORT COAT - STRAIGHT COAT - WIRE COAT
or as they say
IMPROPERLY COATED
PORTUGUESE WATER DOGS