Besides VRBO who's site I find awkward to use, just google for big island condo rental, and you'll find several agencies with inventory - SunQuest, ATR, Prince, Knutsen, others. With negotiation it seems like prices for a decent 1BD can start around $70/nt +13% tax and usually a cleaning fee, on up. $100/nt should get a very nice place, or more bedrooms. The market has been soft. We're 1.5 miles south of downtown and can walk 50 ft from the resort to some excellent diving. The dolphins come by a couple of times, almost every day. Shore diving here rarely involves sand and the entries are often directly into 10-30 ft of water, so as long as you pick the spot well, it's not rough if the seas are down (this is very important!!). We're finishing up 6 weeks and about 50 shore dives, and the seas have been calm enough to dive almost any spot for most of the last 4 weeks straight. You can get a good forecast at
MagicSeaWeed . We haven't noticed any difference between 0.5 and 1.0 ft forecast swells (it's been forecast 1.0 for the last week, but in reality it's been better than many of the prior two weeks' 0.5 days, and almost lake-still much of the time!), but above that, the options close down quickly, that we've observed. There are condos all the way from downtown south for about 8 miles, so you could stay within easy walk of Jack's and one or two others, but if you have a car, I'd start looking right at the south edge of Kailua Bay, on down to the end of the developments in Keauhou.
I'll recommend
Big Island Divers as well - the shop is on the north edge of town near the Target mall - who IMO have the best shore dive rental prices and policy of the ones I checked with, and are all very nice and helpful. They have two boats and run Manta and Black Water dives like some others. They used to schedule 3 tank dive days but don't appear to do that formally any longer.
The dive ops seem to favor a handful of the 50 or so moored dive sites, maybe a third of which are also shore accessible (get a car with good ground clearance for the unimproved shore roads), and I don't think there's hardly one of those moorings that's much more than 50 yds from shore. Since with minor feature variations, many sites look similar and have the same critters, I recommend shore diving for longer and better (to my way of thinking) dives. The big dive ops here all run master-lead dives that I know of, not sure if there are any that let you go your own way. There's usually little risk of current or disorientation, that I've found. Most dives can be 40 ft or less if you like, or deeper - the steep slope at many sites is within ready swimming distance of the shore. The walk from the car to the entry can be less than 100 yds at most sites, often just a few feet. It's seemed unusually cool here this time, so the suit-ups and walks have been even pleasant.
I should emphasize: SHORE DIVING ENTRIES AND EXITS CAN BECOME VERY HAZARDOUS WITH JUST A SMALL CHANGE IN SEA STATE at many or most sites. Conditions can change within the day just from winds alone. If you have any concerns about a site or your ability to judge conditions, ask the dive shop for help in selection, or take a charter.