Since the early 1960s when I chatted with the Cousteau crew about the
"Amphatrite" (SP) I have been a fan of the inflatable boat. I owned a number of inflatable all were used solely for diving...free diving spear fishing & Scuba.
I currently do not have an inflatable but I have owned several Zodiacs and most recently a Achilles. They ranged in size from about 8 feet to about 12 feet. Every one I owned I over powered it by a step or two..If it required a 25 Hp - I used a 35 Hp etc to over come the general over loading associated with recreational diving.
I have used them up and down the California coast and abused them for weeks on end on the many trips to isolated remote beaches of Baja with not any unforeseen problems. All that I owned were very dependable and above all rugged.
I would suggest that you purchase the smallest possible boat with a hard floor that will suffice for your intended activities, purchase a large engine to over power it, and if Baja bound obtain some sand wheels for launch and retrieval.
The best most reliable dealer I have found was in Oxnard or Ventura. Purchased a number of items from him and had some repairs -expensive but very professional.
He marketed an inflatable made in South America; the "Carribe" (?) which appeared to be ideal for recreational diving.. White in color it had high gunnels, large pontoons and rugged construction..might be worth the trip to see his inventory.
With all that is written please bear in mind an inflatable boat is a wet boat..It can be very wet and very cold on a December night when motoring into the wind..
Good luck,