You can take a boat trip to the active volcano of White Island though it's low down the danger rating list, it's still a volcano & you can never tell since by nature the're unpredictable. You've a good chance of seeing dolphins on the way. You can do jet boating trips. Mr 'Jim will fix it', who drove me to meet the boat for White Island boat, could arrange anything. You can even take a flying lesson, it's a hours flying lesson to view the volcano at Rotorua and return.
Please view this website, you should find everything you need to know here: http://www.bayofplentynz.com/ almost 6 years ago