- backwaters
- bacterium
- BAH
- banks
- barbel
- basad
- basibranchials
- bathyale
- bathypelagic
- beak
- beard
- behavior
- beloniformes
- benthic
- benthopelagic
- biarmed
- bicoloured
- bicuspid
- bifid
- bifurcate
- bilateral
- bilateral compressed
- bill
- billfishes
- bilobate
- bilobed
- binocular
- biologist
- biology
- bioluminescence
- biomass
- biota
- biotic
- biotope
- bipolar
- biserial
- bisubtropical
- bitemperate
- bivalves
- bladder
- blastoderm
- blastopore
- blastula
- blood
- BMNH
- BOC
- bone
- bony fishes
- bony stay
- border
- boreal
- boreoaectic
- botanist
- bottom living
- BPBM
- brackish
- branched rays
- branchial
- branchiostegal membrane
- branchiostegal rays
- breast
- breed
- breeding
- bristles
- brood
- brooding
- bryozoa
- buccal
- bucklers
- buffer
- Bulb
- burrow