It seems to me that it could be Doris bovena, Doris kyolis or Doris ilo, but the colors are changed in the photo, which is not very sharp anyway, sorry.

Check out iSpot to see if you can find a match

I have no idea I am a geologists Sorry

It seems like Doris species. You will have to compare the identification characters of different species of the genus to confirm the species. Colour photo guides may also helpful.

Definitively it belongs to Doridacea family, but you need to look for some branchial features to be sure of the species, another related genus is Hypselodoris; this late distributes both sides of Atlantic ocean and are not uncommon.

There are at least two pages with good information about Doridacea that can be useful to narrow the errors in photographic identification (links below).

Hope this be helpful to you.

http://opistobranquis.info/en/guia/nudibranchia/euctenidiacea/doridacea/#gsc.tab=0

and

http://www.seaslugforum.net/

or

http://www.seaslugforum.net/showall/hypspict

best regards

Thank you all for your answers, I will continue looking for the species using the information you gave me.

Best wishes,

Enrique

On first inspection it appears to be Doris granulosa (Pease, 1860) syn. Doriopsis pecten. You will find more detail on this possible animal by searching Doriopsis pecten. This animal is characterised by the distinctive gill pocket which appears as a transverse line across the dorsum, the pappilose process on the notum and is often associated with the blue sponge Terpios sp. This species is described from the Indo-West Pacific so the Gulf of Mexico is outside its described range - but this may indicate a range extension. http://www.seaslugforum.net/find/doripect