The Bay of Islands is approximately 4 hours north of Auckland by car. Alternatively, you can fly to KeriKeri from Auckland airport--although you will still be approximately 40 minutes from Paihia.

If you are driving straight to Russell, you can take the more direct route of SH1 and cross on the vehicle ferry at Opua--or take the coastal road, via Whakapara & Oakura. The coastal road is a spectacular drive. DO NOT follow this route on your first day after a long flight.  It is very windy and needs your full attention. Even SH1 all the way to Opua is quite windy in parts, so you should think about stopping off around Whangarei for your first night.

The vehicle ferry between Russell and Paihia leaves from Opua (15 minutes south of Paihia) and takes about 15 minutes.  Line up in the queue and pay once you are boarded. In the height of summer you may have to wait for 15-20 minutes, although there are two ferries operating. The passenger ferries (fast & slow available) leave on a regular basis from both the Russell & Paihia wharves.  If you are planning on returning after an evening meal at your destination, be sure to let your restaurant know that you will be crossing, so that you will be finished in time for the last ferry.

Paihia is the “gateway” to the Bay of Islands, and there are plenty of accomodations and restaurants.  Russell is less touristy than Paihia, a lot quieter and more quaint; history buffs will find much of interest in this first capital of New Zealand, and in the nearby Waitangi Treaty House, where the document which laid the foundations of modern-day New Zealand was signed.  

 Both Paihia and Russell are located on the water and have nice little bays for swimming, but the best beaches and bays are out around the islands.    Most of the boat trips leave from Paihia's wharf and stop at the Russell wharf to collect passengers. Yachts at anchor- BOI 

You can swim with the dolphins, check out this site;  It is recommended that you book once you are in NZ. Depending on how long you are in the Bay of Islands area book early on in your visit, so if the weather is bad or on the off-chance they don't find any dolphins, you can make use of the offer to go again for free.  If you wait unitl your last day, if the trip isn't successful you will be disappointed.

. Dolphins riding the bow wave Dolphin watching

Take a day trip to Roberton Island from Paihia - the sand is white and the sea is blue. There are two small ocean pools where you can snorkel. The Department of Conservation have put labels underwater on the various seaweeds and shellfish so you know what you’re looking at. At the height of summer there are dozens of visiting yachts and boats anchored here for the day, it is an excellent bay for swimming, kayaking and just plain sunbathing! The photo of Roberton is one that a lot of companies use for their advertising, check out the Fullers link below.

. Roberton Island

You may also like to do an overnight boat cruise, this one is very reasonably priced

The most popular boating experience is “The Cream Trip."  These large catamarans travel out to Cape Brett and the Hole in the Rock. The boats are quick and fast and will give you a much broader view of the islands, you will visit all the popular ones and some of the boats stop off for lunch in a quiet bay. You get a good commentary of the history around the islands as well. They visit the Hole in the Rock (and pass through it 9 times out of 10) at Cape Brett. They are fast they will get you out there quickly for a look and then back into the islands for lunch etc, they also can go very close into the shore of a lot of the bays for a good look. If you want a real thrill check out the Excitor, exhilarating!   Fullers web site-   The photo on their home page is of Roberton island, you can see the 2 ocean pools that are wonderful for kids to swim in (unless there’s a big easterly swell)

Fullers Catamaran-   Walking track-Moturua Island

Norwegian Bay  Honeymoon Bay

BOI Sunset  Resident stingray

Some of the above information has been collected from previous posts, many thanks to Hokianga Farmer, Lupton Lodge & NettieNZ and other TAers who have contributed.