What is the origin of the idiom "dive in headfirst" and when to use it?

The exact origin of the idiom "dive in headfirst" is not well-documented, but it likely developed from the literal act of diving into water. It has been in use for many years and became more widely used in everyday language during the 20th century. This expression has been used to encourage or describe someone who is eager and willing to take on a challenge or embrace a new endeavor without reservation.