A sonic depth finder is a valuable tool used to measure the depth of water. However, there are several synonyms for a sonic depth finder that are commonly used among sailors and other water enthusiasts. Some of these synonyms include echo sounder, depth sounder, fishfinder, and sonar. Each of these terms is used interchangeably to refer to the same device. While they may have slightly different technical meanings, they all accomplish the same function. Whether you're a professional sailor or an amateur fisherman, having a sonic depth finder on hand can make all the difference when it comes to navigating the water.