Think this might be a hazard, then?
That was my first thought as well, it's more a hazard than a monster in 3rd edition terms. A good start would be the SRD entry for green slime:
Green Slime (CR 4)
This dungeon peril is a dangerous variety of normal slime. Green slime devours flesh and organic materials on contact and is even capable of dissolving metal. Bright green, wet, and sticky, it clings to walls, floors, and ceilings in patches, reproducing as it consumes organic matter. It drops from walls and ceilings when it detects movement (and possible food) below
A single 5-foot square of green slime deals 1d6 points of Constitution damage per round while it devours flesh. On the first round of contact, the slime can be scraped off a creature (most likely destroying the scraping device), but after that it must be frozen, burned, or cut away (dealing damage to the victim as well). Anything that deals cold or fire damage, sunlight, or a remove disease spell destroys a patch of green slime. Against wood or metal, green slime deals 2d6 points of damage per round, ignoring metal’s hardness but not that of wood. It does not harm stone.
So how about:
Black Slime (CR 4)
Also called oil slime, this marine hazard is an aquatic variety of green slime. Black slime devours flesh on contact, but unlike green slime it can not dissolve non-living materials like metal or wood. Looking much like a small oil slick, black slime floats on the top of the ocean, attacking creatures with which it comes into contact, reproducing as it consumes organic matter. It has no means of self-propulsion, moving about only at the whims of the winds and the waves.
Black slime has a limited ability to change its basic shape - it can form strands that float below the surface of the ocean. These strands act like the tentacles of a jellyfish, allowing the slime to adhere to any fish that might pass beneath it. Black slime attacks anything touching its upper surface as well. A swimmer bumping into a floating patch of black slime finds himself coated in the stuff, as does a sea bird landing in it.
Black slime is a colony creature but has no intelligence of its own. Like other slimes, it has a limited awareness of the world around through its ability to sense vibrations, which allows it to target prey. As the colony absorbs other creatures, it grows in size, eventually splitting into two approximately equally-sized colonies. Several colonies are often found together, but this is merely the result of the tides. Every once in a while, colonies drift together and form an extra-large floating slick of slime, but these do not stay together long, nor do they merge into a single creature - once separated, black slime does not unite together again.
A black slime colony occupies a single 5-foot square and deals 1d6 points of Constitution damage per round while it devours flesh. On the first round of contact, the slime can be scraped off a creature (most likely destroying the scraping device), but after that it must be burned, or cut away (dealing damage to the victim as well). Black slime is a form of plant life and is subject to spells affecting plants. It is immune to cold damage, but fire damage or a remove disease spell destroys a patch of black slime.
Black slime is sticky and highly flammable, doing damage equivalent to alchemist's fire when alight. Unscrupulous sailors and pirates may harvest the stuff to use as a weapon. The slime, when carefully poured into a glass vial, can be stoppered and stored for 4d4 days, until the isolated slime starves. The vials need to be a transparent material such as glass because black slime needs sunlight to live, dying after 24 hours in darkness. Thus, opaque pottery flasks are unsuitable containers for storing black slime alive. The vials are catapulted onto enemy ships to break and splash all over the enemy crew, or can be sent hurling at the enemy with a flaming wick attached, creating an organic version of the Molotov cocktail.
Most of that is just a merging of the green slime SRD and extracts from the Dragon write-up, but I've added an explanation as to why they require glass vials for storage
in italics.