Hawaii is one of the most isolated group of islands in the world. It's a long way to Hawaii from mainland USA with nothing but open sea between. Winter storms can bring about rough seas and cyclones are a threat in late summer.
Fully serviced marinas are at Honolulu and KoOlina on Oahu, Lihue on Kauai, Honokohau (Kailua) on the Big Island and Lahaina on Maui. Hanalai Bay and Poipu on Kauai are also popular berthing spots.

Renting small hoby cats is more practical and can be done at most major resorts around the islands.

Weather

The climate is subtropical in the low coastal areas and temperate in the mountains. There is no rainy season but showers, sometimes downpours, occur in winter. The islands are under the influence of the NE trade winds and are only rarely affected by tropical cyclones.

Regulations on anchoring:

The Department of Land and Natural Ressources (DLNR) has established rules that all boaters in Hawaiian islands must follow.

The first rule to remember is that you can anchor in any anchorage for 72 hours without checking in. The one exception is that you must check in immediatly whenever you enter a harbor with a harbormaster on site, such as Ala Wai, Ke'echi, Wai'anae, Hale'Iwa, He'ela Kea, Kaunakakai, Hilo, Honokôhau, Lahaina, Ma'alaea, Mânele, Kahului, or Port Allen.
After the first 72 hours is up, boaters are required to move to another anchorage or even to another part of the same anchorage.

The exceptions to this right to anchor in any anchorage for 72 hours are the areas that are part of Marine Conservation District or Natural Area. All or part of some bays have been placed in Conservation District because the heavy traffic and the delicate ecosystem on the bottom of the bay required intervention on the part of the State of Hawaii.

Boaters may not anchor in part or all of the following bays:

Hâ'ena bay: boats may not anchor inside the reef overnight
Hanauma bay: no boats allowed in this bay
Hulopo'e bay: no boats allowed in the bay
Kealakekua bay: boats may not anchor in Subzone A
La Perouse bay: boats may not anchor in the western half of the bay
Waikiki anchorage: no boats allowed within 4 mile of the beach.

When boaters visit small boat harbors in Hawaii, they must obtain a permit from the harbormaster and pay a daily fee, as is the case in harbors anywhere. The difference here is that the facilities are not the plush ones some boaters might be accustomed to elsewhere. Although some might complain about the facilities, the low daily rate charged to visiting boaters more than makes up for any shortage in facilities.