Jennifer spotted this Blue Swallowtail SeaSlug
Chelidonura hirundinina all of about 20mm in length while diving off Luadi in PNG.
Closely related to Nudibranchs, this Opsithobranch lacks the characteristic cephalic tentacles and branchial plume of its close Gastropod relative. It is however every bit as stunning. Have a look at
SeaSlug.net for more info.
Until the next post, take care out there and keep diving ( if that's what you do! ) ...Robert