When it comes to describing "good penetration", there are several synonyms to choose from. Some options include profundity, thoroughness, depth, insight, understanding, comprehension, and acumen. These words all convey the idea of a thorough and effective penetration into a topic or subject matter. Additionally, words like mastery, expertise, and proficiency can also be used to describe a high level of skill and knowledge. The key is to choose synonyms that accurately convey the specific type of penetration being discussed, whether it be intellectual, physical, or emotional, and to use them in a way that is clear and concise.