Certification for what is called "Deeper Diving"

I was going to be diving at:

Grand Cayman, B.W.I.
Roatan, Honduras
Belize, Central America
Cozumel, Mexico

"Open Water" certification takes you to only 65 feet.

I anticipated wanting to dive deeper and with safety.

Advanced Open Water certification is for what is called "deeper diving".

Deeper Diving certifies you to 135 feet.

That is as deep as you may dive without calculated mandatory decompression stops as part of your ascent.

Deeper diving also requires important additional training. New equipment needs and special other differences will be experienced by the diver.

At 130 feet the pressure is equal to five (5) atmospheric pressures.

All of the areas of concern for safety at more shallow dives are magnified (nitrogen narcosis, for example).

There are also some new issues. For example, oxygen becomes toxic to the central nervous system at very deep depths (deeper than the recreational diving limits).