I haven’t visited Hawaii yet, but I’ve included community reports from those who have.
Oahu, 2022: Sierra Foley & Teddy Relan, 5 days & 4 species including Hawaiian Monk Seal and Spinner Dolphins.
Kauai, 2020: Justin Brown, and useful information on seeing Hawaiian Monk Seals.
Kauai, 2019: Cheryl Antonucci’s report of multiple Monk Seals and some Spinner Dolphins.
Maui, 2015: Vladimir Dinets’s notes on various mammals occasionally seen on Maui (which is a bit of a mammalian desert it seems).