A sounder tells you two hard facts: depth, and how hard the seabed is. Everything else on the screen is a pattern you learn to read. In Kuwait the bottom flips from soft mud in the bay to rock and coral heads offshore, and that difference decides whether you anchor on fish or on empty water.
A thin, bright, sharply defined bottom line means hard ground: rock, reef, compacted sand. A thick, soft, fading line with a wide band beneath it means mud or loose silt, which covers most of Kuwait Bay and the Jahra flats. The gap between the main line and the second echo is the soft layer, so the wider that gap, the softer the ground and the faster your sinker disappears into it.
A consistent second line under the bottom is usually a soft layer, or fish pinned to the seabed that never rises into an arch. Fish sitting hard on the ground thicken the bottom trace or show as a small lump attached to it, not as a clean arch. Over mud, schools of small bait read as a broken, scattered line, which looks like noise until you learn that the noise is life.
An arch is a fish that passed through the cone. A full, symmetrical arch means it crossed the centre of the beam. A half arch at the edge of the screen means it only clipped the side, so it is still a fish but you cannot judge its size. A bigger arch is not automatically a bigger fish: depth and the seconds it spent in the beam both change the shape.
Shuwaikh channel: hard edges and strong tide lines that draw jagged teeth along the bottom. Shuaiba: rock and rubble patches beside smooth sandy lanes, where any arch above the hard patch is usually a fish holding on it. Fahaheel: reef edges drop sharply, and fish sit on the edge rather than in the middle. Bubiyan and Jahra: soft and shallow, where the difference between one metre and two decides where you stop.
The picture lags with speed, and the depth on screen is what already passed under the hull, not what is ahead of you. In shallow water and around reef, keep your eyes on the sea and on the navigational tools in the app; the sounder assists, it does not drive. Write your working depths and marks into the B7R catch log so you can find them again without hunting.
All of it gets easier when the Shuwaikh and Shuaiba tides, the sea state and your trip notes live in one place. Download B7R free on Google Play and start reading your bottom properly: https://play.google.com/store/apps/details?id=com.q8dm.b7r