In the first half of the 19th century natural historians aimed to demystify the oceans. This endeavour was complicated by the fact that the sea is an extreme environment as far as the human physique is concerned. Appropriate research sites were geographically and methodologically inaccessible to the natural historians who lacked sufficient practical know-how to undertake scientific observations. Directing the scientific gaze into the deep required some visual aid. Early marine zoology research relied on the practical know-how and observations of professional sea-farers and objects that were found near or on land. In this paper, I discuss the practical reality of marine field research in an area where three ocean activities – research, work and play – intermingled in a social as well as epistemological sense: Gullmarn, a fiord on the Swedish west coast, where the Baltic Sea meets the Atlantic. In the 1830s, this traditional fishing region attracted its first marine researchers. From then on, international and national scientific interest for Gullmarn’s fauna grew. In 1876/77 a research station was established on location, but during the preceding decades, visiting researchers were dependent on the knowledge and equipment of local fishermen and other sea labourers. Science historian Helen M. Rozwadowski has argued that 19th century knowledge of the oceans should not only be understood from work as a central category, but also through ‘play’, i.e. beach tourism and recreation. Indeed, parallel to increased research, Gullmarn also became increasingly popular as an ocean resort for well-to-do city dwellers with an interest in the sea. Although with an ocean in common, the participants in this process of knowledge-making represented social and epistemological categories with each their own vested interests in and motives for understanding the sea and its inhabitants. With specific focus on the research of marine zoologist Sven Lovén (1809-1895), I will discuss the nature of the diverse roles and interests by Gullmarn, and which consequences it had for knowledge-claims about and definitions of regional marine life. I will also discuss role dynamics, i.e. how Lovén’s research was conducted in regards to aforementioned categories and social status.