This little member of the Limapontiidae family (order Sacoglossa) has a few look-a-likes. Placida Kevinleei can also be found on Hawaii, but it has less pronounced white lines on its rhinophores and tends to be smaller.  The two animals documented here, however, appeared to be no more than a couple of black dots on their host Derbesia  algae and were approximately 7-10 mm. For more images and information, check out Sea Slugs of Hawaii.  And yes, this nudibranch was named after President Barack Obama for a reason: his dedication to reducing global carbon emissions and his 2016 proclamation to expand the Papahānaumokuākea Marine National Monument.