A logical approach to dealing with fear in diving depends on understanding the causes and dealing with them rationally.
Fear is a logical response to the unknown. Understanding this unknown turns fear into respect.
The cause is unknown, not the actual danger. The depths in which you train are safe by their rules. Know the rules and change fear.
Study the organisms before diving. Whoever knows that the reef shark does not attack fears it less.
Ignorance amplifies fear and knowledge adapts it to healthy respect.