… range, consists of a marked 30-metre braided line and a conical, noble plummet made of heavy bronze or grey cast iron. At the bottom of these plummets, a small hole can be found. Some tallow can be pressed into the hole, so when the plummet touches the seabed, sediment will stick on the tallow. Based on the soil sample, seabed condition and the ship's position can be localized. On older yachts, on traditional boats and GRP classics, analogue echo sounders are often still in use. These flashing sounders indicate the depth using a rotating light-emitting diode. A type of this proven and inexpensive device class is still available and can be considered as a kind of retro navigation device. You will also find corresponding depth sounder transducers and installation kits, which can be used for almost every common brand of these device classes (NASA, ECHOPILOT, SEAFARER).