Strange Stones VIII

A few weeks ago, Beatrix hired a fishing charter for Lake Tempest. She asked the crew about strange stones before they left. A couple of the older hands said that they found a few strange stones on a variety of fishing trips. After a lot of disagreement, Captain Logan suggested the best strategy would be to follow the flow of the water and search the lake, the river, and the ocean. Since then, Beatrix has fished and hired charters every day with no success. Will you try the lake?