* Plop! - This is the most common and straightforward choice. It captures the soft, sudden sound of the pebble hitting the water.
* Plunk! - This adds a bit more weight to the sound, suggesting a slightly larger pebble.
* Sploosh! - This emphasizes the ripple effect of the pebble hitting the water, creating a more dynamic sound.
* Tinkle! - This option suggests a smaller pebble that makes a light, tinkling sound.
The best onomatopoeia depends on the specific size of the pebble, the depth of the lake, and the overall feeling you want to convey.