🔍 Key Concepts

• Fathometer (echo sounder) operation—how sound pulses reflect off different types of seabeds • Differences between soft bottom (mud/silt) and hard bottom (rock/sand) echoes • How multiple or weak echoes might appear on the depth display

💭 Think About

• Think about what happens to a sound pulse when it hits a very soft, absorbent bottom like mud—does it bounce back strongly, weakly, or possibly in more than one layer? • Consider which choice best matches a situation where the sound energy penetrates into the bottom instead of reflecting sharply from a hard surface. • Which answer would you expect if the fathometer is still working correctly, but the bottom type is causing an unusual echo behavior?

✅ Before You Answer

• Verify how soft, muddy bottoms affect the strength and clarity of the returned echo compared with hard bottoms. • Consider whether a complete loss of reading is likely if the transducer and electronics are functioning normally, even over mud. • Ask yourself if a double or split echo can occur when the sound pulse interacts with layers in a soft bottom like mud.