How many metres deep can a sperm whale dive?

How to get close to this number

A useful way in is to ask what the animal is diving *for*. Sperm whales hunt squid, and squid live below the point where sunlight gives out — so the dive has to clear the entire sunlit layer of the ocean and keep going into permanent darkness. Once you frame it that way, the answer has to be measured in kilometres rather than in hundreds of metres, which rules out most low guesses immediately.

The trap is human scale. Recreational scuba tops out a few tens of metres down, military submarines operate a few hundred, and those are the only depth numbers most people have ever heard. Reaching for them puts you one or two orders of magnitude short. The whale is not doing a deeper version of a human dive; it is doing something humans cannot do at all without a pressure hull, and the figure has to reflect that gap.

The number is also a working maximum rather than a hard limit. It comes from tagged animals on foraging dives, and individual whales have been recorded deeper; what gets published is the depth the species routinely reaches, which is the honest figure to quote because it describes normal behaviour rather than a single outlier. Tagging coverage keeps improving, so this is the kind of figure that gets revised as instruments get better, not as the whales change.