- Pacific Ocean
- pagurid
- palaemonids
- Palaeozoic
- palate
- palatine
- palatoptergoid
- Palearctic
- Paleocene
- paleoecology
- paleontology
- pantropical
- papilla
- paraphyletic
- parasites
- parasitism
- paratype
- parietal
- parthenogenesis
- parturition
- paternal
- pathogen
- pectinate
- pectoral
- pediform
- peduncle
- pelagic
- pellet
- pelvic
- pennant
- pennate
- Pennsylvanian
- pentagon
- penultimate
- pericentric inversion
- periphyton
- peritoneum
- perivisceral
- perivitelline
- permutation
- phagocytosis
- pharyngeal teeth
- pharynx
- phenetic taxonomy
- pheromones
- photogenic
- photophore
- phyletic
- phylogeny
- phylum
- phytal
- phytophagous
- phytoplankters
- phytoplankton
- pigment
- pilose
- Pisces
- piscivore
- piscivorous
- pistol crabs
- planktivore
- plankton
- plant
- Pleistocene
- plesiomorphy
- pleurotremata
- plicae
- Pliocene
- plumose
- poikilothermic
- polar
- polyandry
- polychaetes
- polygyny
- polyhaline
- polynemids
- polynya
- polyphyletic
- pond
- pool
- population
- post-spawning
- postadult
- posteriad
- posterior
- postlarvae
- postmetamorphic
- postorbital
- pouch
- pout
- ppt
- prawn
- pre-anal
- prebranchial
- predator
- predorsal
- premaxillae
- prenarial
- preopercle
- preoral
- preorbital
- prepectoral
- primary production
- primordial
- process
- procumbent
- procurrent rays
- prodrome
- prolarvae
- prolification
- propagate
- propagation
- protandrous
- protoctist
- protogeny
- protractile
- protraction
- protruded
- protuberance
- proximal
- pseudo-oceanic
- pseudobranch
- pteropods
- pterygiophore
- punctate
- pungent
- pupil
- pyloric caeca