I live just up the hill from the bay. I haven't swam with them in 3 or 4 years, but I hear the bay is getting less reliable in the morning because of the heavy kayak traffic.
Your best bet is to drive down Napoopoo road around 7:30 to 8:00 am and hang a right at the old wharf it runs into. The road ends about a hundred yards later at a small park with a large heiau (stone temple). You will be at the bay and can watch from there to see if the dolphins are in. They generally like to hang about 300-800 yards from the beach area but I've seen them within 50-80 yards on occasion. If they are in they tend to be most active between 7:30 and 9:00 or so. By 10:00 am they are heading deep to rest.
Here's something you do need to know. Technically they fall under the marine mammal protection act and you aren't supposed to swim with them. There's getting to be more and more niose about enforcement. They've had meetings in Kailua and basically told all the commercial swim with dolphin tours to cease and desist. Most of the dive operators are no longer putting their customers in in front of dolphin schools anymore either. They haven't been enforcing anything on individuals who decide to try a dolphin swim on their own yet, but you never know when they may start.
As for dolphin ettiquette, from back in the day when I have done it a few times, it is best not to approach them....they'll move on. The best place to put yourself is about 50 yards away from them and let them come check you out. This is difficult to do in Kealakekua due to all the swimmers and kayakers who will be chasing the dolphins. If you can get there when there aren't too many others in the water and the dolphins are active (if you don't see dolphins, don't bother, better chance of seeing a tiger shark) you'll have a better chance at having them come to you.
My best success was a few years back at Hookena Beach when a couple of us just went out in the general area the dolphins were hanging and then did a survival float. They began milling around us for 5-10 minutes at a time then would leave for 5-10 and them join up with us again. By milling around I mean staying between 10 and 60 feet of us for minutes at a time rather than the few seconds you'll get if you try to swim. The guy I was with got 52 minutes of video in around 2 hours time. He was stoked. Swimming tends to put them into a mode where they make large figure eights and you'll never keep within sight of them for more than a few seconds.
I've had several people tell me they love following freedivers. Apparently they are curious about humans who do atypical underwater behaviors. One of my friends gets them to come within inches pretty much every time he jumps in by going down 15 feet and then doing pseudo ballet pirouetting type of movements. He's had visibly aroused males rub up against him when he's done this. Don't know if it is a love or hate relationship there though. Being nice and quiet or doing the strange underwater movements seems to do well. I've watched people do all sorts of singing baloney, but I've never seen them be more successfull than any other person who just swims after them and gets a 10 second glimpse, at least they had fun though.
If nothing is happening at the bay, head on down to the Place of Refuge (just 5 miles down a one lane road from the bay). Sometimes the dolphins hit there too, great snorkeling even if no dolphins. Hookena often has dolphins on sunny afternoons and that's where the locals swim with them most often.
Remember, these are wild animals and although I've never heard of troubles locally, they could easily dispatch a human if things didn't go as expected.
have fun
Steve
