2. The islands shelter and protect the waters for the whales, keeping them at shallow depths. Maui is located in a little island cluster with Lanai, Molokai, & Kahaloowe...with those being in such close promiximity they form a shallow basin for the whales to enjoy juxtapose that with the surrounding pacific ocean where depths average at 1 to 3 miles. Humpbacks seem to prefer "shallow/protected" waters and spend the majority of their lives in waters that are 300 feet or less.
3. Another reason to come to Maui is that Hawaiian waters are virtually predator free for the humpback whales. Their only real predators are a few shark species that will feed on the sick injured or young whales and then the Orca/Killer Whale.
There are rarely orcas in Hawaii, since they like colder water. In Alaska humpbacks encounter orcas on a regular basis and around 20% of humpback whales bear scars from orca attacks. Sad huh?