Sure....Please find attached an IOK file that contains an example of custom entity extraction.

In this example I have created a simple source that contains 3 text records. In the "Text mine" block we have specified that we want to extract the custom entities "shark", "great white" and "carcharodon carcharias". In the preview panel we can see that all 3 entities appear in the first record, none in the second and "shark" appears in the third. Let us know if you have any further questions.

Thanks for that and the info about the sharks.