Was just there 2 weeks ago. Will be writing a trip report after this post. Dove with Fathom Five which is about a 30 minute drive from where we stayed in Kapa’a. They were easy to deal with in booking the dives. The crew on the boat was knowledgeable, safety conscious and fun. They changed over tanks during surface intervals, provided snacks and drinks (coffee at the shop), and took care of our gear since we did several days of diving.The maximum number of divers is 6. Parking is at their shop and they shuttle you to the boat in a nice van. Would definitely dive with them again.
Regarding Tunnels Beach, the road was still closed so it was out as a dive site. Nihau is a 7-9 hour day. I was told that it is about a 3 hour boat ride there and longer to get back, but there is an op that uses a Zodiac and can get you there in about 45 minutes.
Koloa Landing is a shore diving site. Just a note - I took only my full foot fins so had no boots. You have to walk out a ways before you can swim and the walking is over big rocks. They didn't warn me at the shop so I was barefoot and struggled a bit.