IFREMER and MICREL have developed a new compact and waterproof tension sensor to record force on lines in seawater. Two shackles link the sensor to the line, and it measures the tension over a short measuring period (e.g. 0.5 s). It records measurements on its internal memory. It records, if needed, only the maxima and minima of the tension for a recording period (e.g. 15 min). The advantage is a very low quantity of records for a long working duration, using a small, cheap sensor. A personal computer communicates with the sensor, for configuring and reading the records, through a special induction coil. This induction coil allows a very simple underwater communication without plug connectors. The programming of the sensor from the personal computer includes the definition of the measuring period (from 0.01 s), the recording period, the tension coding (up to 12 bits), and the start and the stop modes. The sensor can be used on different kinds of line such as rope, chain or trawl warp.