In attempting to predict the impact of major ecological or climatic change on livelihoods, insights can be gained by looking at communities who experience extreme seasonal or annual variation. Here, we compare the ecology, economy, and social network of a community of traditional fishers in the Brazilian Pantanal between the dry season and the flood season in which their wetland ecosystem is transformed. Using data derived from satellite imaging we show that during the flood season of 2019 the total amount of open water accessible to fishers more than doubled and led to drastic qualitative changes. We show that although fishers adapted to this extreme seasonality by changing where, how, and what they fish between seasons, the structure of the social network in our study community did not differ. We argue that strong networks are especially important in social-ecological systems with extreme seasonal changes. More generally, we suggest that case studies of seasonal adaptation such as ours can contribute to a broader understanding of how communities may be able to successfully adapt to novel social-ecological changes.