Nudibranchs & sea slugs

Nudibranchia

The jewels of the sea — nudibranchs come in every colour combination imaginable and reward slow, careful searching. Check under overhangs, on sponges, and along hydroids. Once you spot your first, you'll start finding them everywhere.

Last updated April 2026

Spotted sea slugPeltodoris atromaculata30 photos

Up to 12 cm5–40mRocky reef

A flat, oval nudibranch — creamy white to pale yellow body covered in distinctive dark brown or black spots and rings. Looks like a cow-print cookie.

Glides slowly over rocky surfaces grazing on sponges — easy to photograph thanks to its slow movement and bold pattern.

Observed at

Las Planetas(Sant Feliu de Guíxols)El negre(Costa del Maresme)Ullastres III(Palamós)El Jardín y La Red(Sant Feliu de Guíxols)Túneles de Port Salvi(Sant Feliu de Guíxols)Dofí Nord(Illes Medes)Bajo de Dentro(Cabo de Palos)Pedra de Déu(Illes Medes)La Garita(Tarifa)Punta Cana(Costa del Maresme)El Trencat(Costa del Maresme)S'Adolitx(Sant Feliu de Guíxols)Els Canons de Tamariu(Begur)Montelivi(Sant Feliu de Guíxols)La Calzada(Costa del Maresme)Bajo Piles I(Cabo de Palos)Dofí Sud(Illes Medes)Badalona(Barcelona)

Violet flabellinaFlabellina affinis23 photos

Up to 5 cm5–40mRocky reef

A delicate, purple-violet nudibranch with clusters of cerata (finger-like projections) along its back tipped in white. Striking color against dark rocky surfaces.

Feeds on hydroids on rocky walls — often found in small groups. One of the most commonly photographed Mediterranean nudibranchs.

Paraflabellina ischitana, Violet flabellina

Observed at

Mar Menuda(Tossa de Mar)Las Planetas(Sant Feliu de Guíxols)Barreta d'en Serra(Costa del Maresme)S'Adolitx(Sant Feliu de Guíxols)Pedra de Déu(Illes Medes)La Calita(La Herradura)Isla de Santa Eulalia(Ibiza)Punta Cana(Costa del Maresme)Montseny(Costa del Maresme)Montelivi(Sant Feliu de Guíxols)Punta de la Mona(La Herradura)Ullastres III(Palamós)Piedra del Hombre(La Herradura)

Cratena peregrinaCratena peregrina13 photos

Up to 5 cm3–25mRocky reef

A terrestrial flatworm that has invaded Mediterranean gardens, but the marine sighting refers to Cratera peregrina — a flat, leaf-shaped worm with brown stripes on a pale body.

Glides across rocky surfaces using muscular contractions — paper-thin and surprisingly fast for a flatworm.

Observed at

La Virgen(Costa del Maresme)Barreta d'en Serra(Costa del Maresme)Dofí Nord(Illes Medes)El Santuari(Costa del Maresme)El Trencat(Costa del Maresme)La Calzada(Costa del Maresme)El negre(Costa del Maresme)

Violet sea slugFelimare picta12 photos

Up to 6 cm5–40mRocky reef

A beautiful nudibranch with a bright blue-purple body edged in yellow-gold, with yellow-tipped rhinophores and gills. One of the Med's most photogenic sea slugs.

Glides slowly over sponge-covered walls — look for the contrasting blue and yellow coloring against dark rock surfaces.

Observed at

Montelivi(Sant Feliu de Guíxols)La Calita(La Herradura)Punta de la Mona(La Herradura)Piedra del Hombre(La Herradura)Las Planetas(Sant Feliu de Guíxols)

Paraflabellina ischitanaParaflabellina ischitana6 photos

Up to 4 cm5–40mRocky reef

A vivid Mediterranean aeolid nudibranch with a translucent pink-purple body and clusters of cerata tipped in white above an orange band. Named for the island of Ischia.

Observed at

Piedra del Hombre(La Herradura)Pedra de Déu(Illes Medes)Punta de la Mona(La Herradura)Las Planetas(Sant Feliu de Guíxols)Montelivi(Sant Feliu de Guíxols)

Pink coryphellaEdmundsella pedata5 photos

Up to 4 cm5–40mRocky reef

A small Mediterranean aeolid nudibranch with a translucent violet body and clusters of cerata tipped in orange-red. Slender oral tentacles and rhinophores. Long known as Flabellina pedata and Coryphella pedata.

Feeds on hydroids on rocky walls, typically in shaded areas — often overlooked due to its small size.

Observed at

S'Adolitx(Sant Feliu de Guíxols)Bajo de Dentro(Cabo de Palos)El Jardín y La Red(Sant Feliu de Guíxols)

Fontandraui's chromodorisFelimare fontandraui4 photos

Up to 5 cm5–40mRocky reef

A vibrant nudibranch with a blue-white body, two bright yellow dorsal stripes, and yellow-tipped rhinophores. Similar to the violet sea slug but with more pronounced yellow markings.

Found on sponge-encrusted rocky walls in the Mediterranean — a prized macro photography subject.

Cantabrian sea slug, Fontandraui's chromodoris

Observed at

Punta de la Mona(La Herradura)La Calita(La Herradura)Las Planetas(Sant Feliu de Guíxols)

Orange godivaNemesignis banyulensis3 photos

Up to 6 cm5–35mRocky reef

A striking aeolid nudibranch with a translucent white body and dense clusters of brown-orange cerata tipped in white. Named after Banyuls-sur-Mer where it was first described.

Feeds on hydroids and anemones on rocky walls — stores stinging cells from its prey in its cerata for self-defense.

Observed at

Ullastres III(Palamós)Punta de la Mona(La Herradura)

Argo doridPlatydoris argo2 photos

Up to 7 cm3–35mRocky reef

A large, flat dorid nudibranch with a firm, leathery rust-brown to reddish body finely mottled with paler blotches and a granular surface. Mostly shelters beneath stones by day.

Observed at

Marina del Este(La Herradura)

White flabellinaLuisella babai2 photos

Up to 3 cm5–35mRocky reef

A small, delicate nudibranch with translucent white body and clusters of cerata. Very similar to Flabellina affinis but typically smaller with subtle differences in cerata arrangement.

Found on hydroid colonies on shaded rocky walls — requires close inspection to distinguish from related flabellina species.

Observed at

La Calita(La Herradura)Punta de la Mona(La Herradura)

Tricolour sea slugFelimare tricolor2 photos

Up to 4 cm5–40mRocky reef

A small Mediterranean chromodorid with a deep blue body crossed by fine cream-yellow longitudinal lines and edged with a bright yellow margin. Slimmer and smaller than the violet sea slug.

Observed at

El negre(Costa del Maresme)Pedra de Déu(Illes Medes)

Villafranca sea slugFelimare villafranca2 photos

Up to 3 cm3–35mRocky reef

A small dark-blue chromodorid speckled with rounded yellow spots and rimmed by a yellow margin. A Mediterranean species of rocky reefs and Posidonia meadows.

Observed at

Ullastres II(Palamós)

Cantabrian sea slugFelimare cantabrica1 photos

Up to 5 cm5–40mRocky reef

A blue-bodied Mediterranean and eastern Atlantic sea slug marked with bright yellow longitudinal lines, found grazing sponges on rocky reefs.

Observed at

Punta de la Mona(La Herradura)

Splendid elysiaThuridilla hopei1 photos

Up to 2 cm0–30m

Observed at

Pedra de Déu(Illes Medes)

ArminaArmina tigrina1 photos

Up to 8 cm5–40mSandRocky reef

A flattened, elongated nudibranch with a velvety texture and distinctive tiger-stripe pattern — dark lines on a pale body. Has feathery gills on the underside.

Burrows in sandy sediments near rocky reefs — occasionally found on night dives crawling across open sandy areas.

Observed at

Badalona(Barcelona)

Orsini sea slugFelimare orsinii1 photos

Up to 3 cm5–40mRocky reef

A small blue-violet chromodorid marked with a fine yellow midline and a yellow margin. One of the smaller Felimare species of the Mediterranean.

Observed at

Las Planetas(Sant Feliu de Guíxols)

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