I am on my 7th boat rigged primarily for diving. It, like all 6 of the boats before it, is a center console - which is my preferred configuration. With 6 divers and their gear, no other style of hull provides enough deck space for all the gear as well as suiting up. I insist that all the tanks have boots on them and I use stern ladders for boarding. I hang a line off both stern cleats with a weight on the end. The lines have gear clips and hang down 25 feet to accommodate both the first and second deco stops. Once you use them, you won't go out without them.
Here are a few shots: First, the boat in the water:
Here's a shot of one of the ladders. There is one on both sides.
Here's my favorite kind of tank rack which is made by Roll Control. I've laid out one of the deco lines on the deck. Three big clips on the line handle everything from scooters to goody bags..