Oops, it doesn't look like 'breathe underwater day' is a national day..

Other days

african immigrant and refugee hiv and hep awareness

African Immigrant And Refugee Hiv And Hep Awareness Day
bow tie

Bow Tie Day
prosecco

Prosecco Day
bounce

Bounce Day
law

Law Day
cuddle up

Cuddle Up Day
nae nae

Nae Nae Day
boy friend

Boy Friend Day
reading

Reading Day
blanket fort

Blanket Fort Day