This article discusses learning that occurred during primary school visits to the UK National Marine Aquarium (Aquarium). Before visiting, children were asked to independently create a drawing of marine life off the Devon coast and a drawing of tropical reef marine life, allowing an assessment of prior knowledge. Post-visit, children created another drawing, with changes between the drawings indicating the degree of learning. Visiting children participated in the Aquarium's guided learning programmes, and children were observed to assess engagement and the contribution of provided information to post-visit drawings. Pre-visit drawings showed limited knowledge of local underwater habitats and less knowledge of tropical reef habitats. However, the comparison of post-visit drawings to pre-visit drawings showed that significant informal learning had occurred as a result of participating in a guided visit, demonstrating that the informal science programme at the Aquarium achieves the goal of enhancing knowledge and understanding of marine habitats. (Contains 4 tables and 2 figures.)