In the UK, most club diving - and, one or two, commercial operations- use RHIB's. Fast, stable, capable of carrying up to 8 divers + kit and able to travel a fair way off shore - with the proper safety equipment, of course! -.
Their main disadvantage is the fact that you are totally exposed to the elements, but in appropriate diving apparel, this is not a major issue. Many UK dive clubs operate all year round in almost all conditions and sea states.

Here in Australia, recreational boating is a big thing, and 5-6m half-cabin or central console aluminium cruisers, or "Tinnies" are very popular.
A boat is on my own -far future- shopping list. At a local boat show last year, I came within a whisker of buying a brand new 6m half cabin cruiser with 250 Mercury outboard, GPS, VHF, all the safety gear and trailer. I was actually sat, pen in hand, with all the paperwork spread out in front of me, the salesman nodding encouragingly when the insistent voice of my conscience broke through my reverie and shouted.
"What the Hell are you doing? ! You haven't got $50,000!".
Thankfully, I listened or my wife would have killed me!