The development of inquiry and project-based materials is challenging in many ways, not the least of which is the design of supports for teachers implementing such materials. We report on the design of educative and just-in-time teacher supports for an online project-based unit in ocean science. The teacher supports were visible as tabs on the student interface and the information provided was divided into four complementary categories: in-class notes, student difficulties, related activities, and resources. These categories reflect the recommendations of Ball and Cohen (1996) and heuristics of Davis and Krajcik (2005) for designing educative curriculum materials. We examined teachers' perception and use of these supports in a pilot study with 18 middle and high school teachers. Our findings suggest that overall teachers found the supports useful although they did not seem to use them in a just-in-time fashion. There were many instances in which teachers' interpretation of the guidance provided and their resulting implementation varied from the designers' intent. Our analysis revealed several themes that account for these variations: differences in the segmentation of the unit activities, underdeveloped or underspecified supports, pedagogical disagreements regarding the implementation strategies, and logistical difficulties. (Contains 3 tables and 1 figure.)