Virtual reality (VR) can provide access to otherwise inaccessible aspects of the world and thus promote science learning. We developed a VR learning tool about the water cycle, with 11 lessons for classroom teaching at the primary level. We assessed prior knowledge before a four-week intervention and learning outcomes directly after the intervention, as well as eight weeks later. A total of 165 children aged 11 to 12 years participated in the study. We manipulated "immersion" by using either VR headsets or computers, and "interaction" by having children either directly engaging with the virtual world or observe an avatar executing the same actions. This design allowed us to test the impact of different levels of immersion and interaction on learning about the water cycle. The results showed an effect of immersion but not of interaction. Children who worked with headsets outperformed children who used computers both in the test immediately after the intervention and 8 weeks after the intervention. Further, we assessed several affective, cognitive, and physical variables during the intervention, including spatial presence, motion sickness, cognitive load, physical load, and children's satisfaction (liking). The findings indicate that immersive VR is a promising tool for teaching science topics about otherwise inaccessible aspects of the world. Future research is needed to better understand how interactive elements can enhance learning in this context.