Cook strait ferries in New Zealand

After living over a year in Auckland(New Zealand) I decided it is time to visit South Island. This means I need to go by ferry from island to another. I was living here for so long and didn’t realize that there are two companies which could take you across Cook Strait. I thought that only Interislander exists. I don’t know for what reason, but at Auckland i-SITEs” was no information about another company – Bluebridge. May be it was because Intersilander was(is) marked as “Qualmark Endorsed Visitor Transport”? But I think it is not fair from point of visitor to hide competitor. Especially then Bluebridge had better deals (30% cheaper then Interislander) at the time I was travelling and I didn’t see anything wrong with ferry I was on. So in case you need cross Cook strait in New Zealand check both companies (Bluebridge, Interislander) for deals and save some money which you’ll definitely will find where to spent in New Zealand.