Pomatoschistus bathi
A 5cm goby that hides in plain sight across Occitanie and the French Riviera, in water around 18C, most of the year.
A tiny, slender fish barely 5 cm long, so pale and mottled grey-brown it nearly disappears against sand or rubble. Look for the way it perches propped on its fins rather than swims freely, and a faint dark blotch pattern along the flank rather than any bold stripe. There's no dramatic colour to key on here, size and posture are the giveaway.
Expect to find it sitting still on sand, rubble, or low reef rather than cruising in open water, usually close to the seabed in the 7 to 14 m range where divers do most of their bottom time. It doesn't spook dramatically but will dart a short distance and resettle if you get too close, which makes it an easy fish to lose track of if you're not looking down carefully. Slow, methodical scanning of the substrate rather than the reef wall is what turns these up.
Like other small gobies, it likely lacks a swim bladder, which is why it perches and hops along the bottom instead of hovering mid-water like most reef fish.
Sightings show no clear seasonal pattern, and its comfort range of roughly 17.5 to 19.8 C sits well within Mediterranean conditions for most of the year, so it's reasonable to look for it on any dive in season rather than planning around a specific month.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably found along the French coast, particularly the French Riviera & Provence and Occitanie, which together account for the bulk of logged sightings. Smaller but consistent numbers turn up in Catalonia in Spain, Sardinia in Italy, and along the Slovenian Coast, so it's a Mediterranean speciality rather than a one-country fish.
Mapping where Bath's Goby is logged…
France is the stronghold, especially the French Riviera & Provence and Occitanie. It also turns up in Catalonia in Spain, Sardinia in Italy, and along the Slovenian Coast.
There's no strong seasonal signal in sightings, and its preferred temperature range of roughly 17.5 to 19.8 C occurs across much of the diving season, so it can be looked for year-round rather than in one specific window.
It's a very small, pale, mottled fish around 5 cm long that perches on sand or rubble rather than swimming freely. There's no bold colour pattern, so size, posture, and habitat are the main clues.
They're small, typically around 5 cm long as adults, which makes them easy to overlook without a close, slow look at the seabed.
No. It's a tiny, harmless bottom-dwelling fish that poses no risk to divers and will simply move off a short distance if approached.
Like many small gobies, it likely has no swim bladder, so instead of hovering in the water column it rests and hops along the bottom using its fins.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Slender Goby
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