Speed 5 ft.
Giant clams simply wait until an unsuspecting opponent swims too close to its current position. When a creature at least one size smaller than the clam swims within reach, it sucks the prey into its interior and clamps shut. It slowly digests its meal and expels any indigestible material (such as metal and stone) into the surrounding water. Air-breathers trapped by a giant clam face the danger of drowning as well.
Str 20, Dex 1, Con 15, Int —, Wis 10, Cha 9
A giant clam has a slow-acting acid that it uses to break down organic matter trapped in its interior. An engulfed creature takes 1d2 points of acid damage each round.
As a standard action, a giant clam can attempt to pull a creature up to one size smaller than itself that is within reach into its interior. An opponent can make an attack of opportunity against the clam, but if it does so it is not entitled to a saving throw. An opponent that does not attempt an attack of opportunity must succeed on a DC 17 Reflex save or be pulled into the clam’s interior. An engulfed creature is subject to the clam’s acid, and is considered to be grappled and trapped within its body. The save DC is Strength-based. A giant clam can be forced open by making an opposed Strength check against the clam’s Strength check. Otherwise, it opens on its own in 1d4 hours.
The rough shell of a giant clam is usually draped with barnacles, anemones, and bits of coral, which help it to blend in with its environment. Creatures must succeed on a DC 20 Perception check to notice a giant clam. Anyone with ranks in Survival or Knowledge (any water- or sea-related skill) can use one of those skills instead of Perception to notice the giant clam.
Environment warm or temperate aquatic
Organization solitary or cluster (2–10)
Giant clams are generally found in coastal waters no deeper than 60 feet from the surface of the water. Many species of giant clams subsist strictly on a diet of sunlight, and as such are never found in deeper waters where sunlight cannot reach. Such giant clams are generally found in shallow seas or attached to coral reefs near the surface.
Some species of giant clams feed not only on sunlight but also on what they can filter from the water, usually small plants and animals, and sometimes the occasional swimmer.
A giant clam moves by pushing out a small “foot” and sliding itself along.