Though my students both were already taking another science course, this was requested. They both thoroughly enjoyed it, so much so that they often do non-required research on marine topics. Neither considered the book difficult, but because they enjoyed the study so much, they retained information and found the reading interesting. They appreciated the range of topics--plants, animals, ecology, geology, geography of the marine world. It is set up like all upper level apologia texts, so the format is easy and predictable. Labs are quite doable.