You can tell for certain that this is <i>Rostanga pulchra</i> by looking at the very unique rhinophores ("deedlers").
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/7232133@N08">Minette Layne</a> from Seattle, Washington, USA
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/7232133@N08/579267816/">Red nudibranch (Rostanga pulchra)</a>