Emergence of vertebrates from water to land, which is thought to have occurred in the mid to late Devonian Period (approximately 390 to 360 million years ago), represents one of the most pivotal events in the history of life on Earth1. Discoveries of new fossils of transitional animals, e.g. elpistostegalian fishes (the fishes most closely related to tetrapods) and early tetrapods, during the last few decades have refined our knowledge on the process considerably, especially on how body structure changed accompanying the habitat transition2–5. These palaeontological studies have also given important clues to unveiling the environmental settings and ecosystem structures of the sites where the transition might have occurred6. The idea that vertebrates abandoned drying-up freshwater bodies in drought to seek larger remaining ponds7 had been widely accepted in the 20th century, but has become questioned by more recent researchers8, particularly after the finding of trace fossils, which dated older than the first known body fossils of vertebrates, and was initially thought to indicate coastal transition to land9. In addition, the new analysis of stable isotopes of the bones of early tetrapods has lent support for the euryhalinity of these animals, which supposedly helped rapid global distribution and colonisation of different land masses10. Even though these palaeontological studies provide the most direct evidence for the process of land invasion by early vertebrates, the fossil records are inherently fragmentary, and some aspects of their ecology remain difficult to reconstitute from these materials. Some of these knowledge gaps may therefore be complemented by studying extant animals that are showing such a transition today.