From bacteria to vertebrates the ability to make decisions underpins life success. Decision-making assumes a capacity to sense, process and respond to information but is routinely linked to animals with a brain. What about brainless animals like sponges —can they make decisions? Deciphering behaviours to address this question is challenging because adult sponges don’t move. However, their motile larvae provide opportunities to investigate behavioural choices. This talk draws on experimental evidence to make a case that the “real estate” of adult sponges is an outcome of “decision-making “larvae. Despite their absence of expensive neural machinery, seen in higher-level animals, to process external habitat signals sponge larvae draw upon forms of taxes to aid how and where they disperse/settle. Examples of sponges using phototaxis, phonotaxis, thigmotaxis and chemotaxis, to navigate to optimal habitat are provided around a narrative of how they might "communicate" with reef environments to make decisions that contribute to fitness outcomes for individuals and populations.