A tiny mark on a chart looks like a familiar object. That resemblance may tempt you to name it immediately. A better study habit is to look up the symbol and keep its surrounding context visible.
Start with the chart’s own information
Identify the producer, product and relevant notes. Then use the reference appropriate to that chart. NOAA’s U.S. Chart No. 1 explains symbols, abbreviations and terms used on nautical charts, including electronic chart presentations.
For a desk exercise, choose one unfamiliar symbol. Record the section and entry in the reference, not merely a cropped picture found elsewhere online. Similar-looking marks may differ in details that a small screenshot obscures.
Make a study card with context
Use three fields: what I initially thought; what the reference says; what detail distinguishes it. An honest first guess helps reveal the feature you overlooked.
Finish by writing a question for your instructor if the reference does not resolve the meaning in that particular presentation. Avoid turning a study card into a standalone navigation aid.
Operational navigation requires appropriate current chart information and competent interpretation. This is a method for learning the vocabulary around it. Pair symbol study with reading depth numbers and their units, so the numbers and marks do not become disconnected fragments.