This dataset contains temperature data acquired between 7 September 2016 and February 2017 using hundred ONE_WIRE_DS18B20S (Maxim IC) sensors installed along a 70 m chain. Sensors are located on the last 50 m of the chain, each separated by 50 cm. The chain is connected to the SeaMoN East frame which is part of the SeaMoN East ecological monitoring node. Data was acquired every five minutes. The chain suffered a malfunction starting in January 2017. Data was cleaned for obvious outliers (temperature > 84°C or < 4°C). Data from 18 to 21 January 2017 should be considered with caution. Data after 21 January 2017 were removed.