The article highlights the historical significance of Zoologica issue 101 (1948), which contains Hans Hass’s groundbreaking doctoral thesis on reteporids (bryozoans) and his pioneering use of autonomous diving equipment for scientific research. It explains how, before the 20th century, underwater exploration was limited to risky methods such as diving bells and heavy helmet suits. This changed when lightweight, self‑contained diving gear became available. Hans Hass was the first scientist to systematically use such equipment (la decade later named SCUBA) during his 1942 expedition in Greece. This allowed him to conduct three‑dimensional underwater research, observe marine life directly, and collect nearly 1,500 bryozoan specimens. His work marked a turning point in marine biology, enabling access to underwater habitats that had previously been unreachable. Despite wartime challenges, Hass continued his research in Naples, Rovinj, Berlin, and Vienna. His dissertation, completed in 1944 and published in 1948, not only analyzed the growth laws of reteporids but also introduced a new scientific diving method. Hass argued that marine biology stations should train researchers as divers - an idea that has since become standard practice. His work is now regarded as a milestone in the history of scientific diving.