Perhaps on a secluded spot along a stretch of shoreline, you may be lucky enough to site a Hawaiian monk seal that has hauled out to bask in the sunshine. If you are lucky enough to site these endangered animals avoid disturbing them by remaining at least 100' away.
In winter months, between November and April, you may be able to site humpback whales swimming in deeper waters. Each winter, these whales travel from Alaska to winter in Hawai'i's warmer waters. Watch for spouts on the horizon.