pel·lu·cid
adjective
definition 1* : allowing maximum light to pass through; transparent.
definition 2: extremely clear in meaning.
example: It’s an invaluable textbook because its pellucid prose makes difficult concepts easy to grasp.
*quotation:
The water in eight fathoms was as pellucid as glass, and we could see the large conger eels twisting about between the stones at the bottom. (Frederick Hoffman, A Sailor of King George)