Linked from
The 15 pages that link to Deep sea, each with the reason it gives.
OceanographyBroader topic: Its scale and remoteness make it difficult to observe directly.
Abyssal zoneNarrower topic: The abyssal zone is one depth region within this broader realm.
Marine fishRelated: Its darkness, pressure, and scarce food support distinctive fish adaptations.
Snipe eelNarrower topic: The deep sea is the environment in which snipe eels live.
Frilled sharkRelated: Its deep-water habitat exposes the shark to darkness and high pressure.