Lindsay says:
This was my first behavior I trained with Reggae from start to finish. I actually trained it twice; the first time I did it, I didn't notice how much his flipper was curling in when he hit my hand-that hurts! So I backed up a few steps and fixed that flipper flat.

See her full blog post with a cool photo here:
http://www.neaq.org/education_and_activities/blogs_webcams_videos_and_more/blogs/marine_mammals/2009/08/140-harbor-seal-high-five.php