Where do you port on Maui? Lahaina or Kahului?
If it's Kahului, it's more difficult since you won't be able to get to the other side of the island in time for the 2-tank morning boat departures on Sunday - most of the Kihei based boats leave between 5:30-7AM. There is good shore diving in the Kihei area - rent tanks from Maui Dreams Dive Co or B&B Scuba in Kihei. About a 20-30 min. drive not counting cruise congestion.
Shore dives on Maui are all on the west side. I only know one dive shop in Kahului.
Scuba Shore Diving Site Listing for: Maui, Hawaiian Islands To boat dive Monday check with B&B Scuba, Ed Robinsons or Mike Severns. They'll all go to Molokini Crater - one of the best dives there. They leave early to beat the tradewinds - B&B is 5:45, Ed Robinsons is 6:30. All check-in at the Kihei Boat Ramp.
If you're porting in Lahaina - you'll miss the morning boats on Sunday - they leave at 7AM. I believe Lahaina is a tendered port also - there's no cruise dock that I'm aware of in that area. Lahaina Divers does a 2 tank afternoon dive on Sunday along the Maui coast (Turtle Town) - shallower but still good dives.
Lahaina Divers - Reservations & Schedule | Scuba Dive Molokini, Maui, Lanai Extended Horizons is another operator that keeps a boat in Lahaina. I don't know their schedule.
Lahaina Divers was also doing Mala Pier at night from their boat - that's one of the better dives in that area. The legal entry is difficult in the daytime, at night it would be really difficult (lot's of submerged coral heads) So check if they're doing that Sunday night. Monday there's a choice of dive destinations - Lahaina runs one boat to Molokini Crater and the other to the Lanai Cathedrals. Both are "signature" dives. Extended Horizons has a smaller boat and only goes to Lanai. Lahaina can have a lot of divers on the boat.
Jack's is a good option for Kona. They're walking distance (5 mins.?) of the cruise pier and with prior set-up arrangements might drive you to their boat in Honokohau Harbor north of town (not where your ship docks). They want you at the shop at 8:30AM.
Shore dives on the Kona side are some distance apart so you'd need a car. If you do, try for Place of Refuge south of town. Shore dive options for both sides of the island - I suspect the Hilo dives are the last two.
Scuba Shore Diving Site Listing for: The Big Island, Hawaiian Islands
For reference, it's a 2+ hour drive between Hilo and Kona - maybe a little more. The Saddle Road between Hilo and Kona also goes to 6600' so you shouldn't drive over it
post dive. I think I'd stay in the Hilo area that day. Or maybe a Volcano tour instead of diving?
On Kauai you port in Nawiliwili harbor. Best bet Thursday is probably a shore dive at Koloa Landing since the boats leave from a harbor near the Poipu area at 7:30AM. I like Seasport Divers, others recommend Fathom Five. Both are near Koloa Landing. Rent a car - a cab both ways would be more expensive. It's a 30 min. drive. Friday dive Sheraton Caverns with one of them, it's the signature dive. I also liked Fast Lanes. Seasport is back b4 noon since they have a 12:45 dive.
One other option might be the Tunnels shore dive on the North Shore - I believe it will be accessible then - it closes in winter when the big waves roll in. One of the lady DM's at Fathom Five/Ocean Quest is one of the better guides for that dive. They also offer it escorted - do that so you don't miss the Tunnels (there's 5 of them). Just a guess, about a 45min. drive from Nawiliwili - could be over an hour. Roads on Kauai are 2 lane in spots.
For how poorly your arrival times mesh with the dive boat departures you might see if your cruise line offers any dives.
Humpbacks should still be around. Off Maui and Kauai - IDK about the Big Island.
