South Seas
The wild heart of Mile Long. At high water Rapids 16 through 19 melt together into the South Seas — open-ocean swell somehow poured into a desert canyon. Towering laterals, exploding crests, troughs deep enough to lose the horizon: this is big water doing its biggest impression of the actual sea, a thousand miles from any coast. As the guidebook puts it, “Rapids 16 through 19 are continuous at high water and are called the South Seas.”
Also known as: The South Seas, Rapids 16-19 (high water)
South Seas refers to the core of the Mile Long sequence — specifically Rapids 16 through 19 — which become one continuous, choppy wave train at high water. The name echoes the ocean-swell character of the waves through this zone and is used by commercial guides and in Webb/Belnap/Weisheit to describe the middle-to-lower stretch of Mile Long where individual rapid identities dissolve into a sustained pulse. South Seas sits downstream of Capsize (Rapid 15) and terminates at Ben Hurt (Rapid 20).
Difficulty
Class III to IV+ depending on flow. At moderate flows the four rapids run as distinct drops with recovery water between; at high flows (roughly 30,000+ cfs) the eddies flush and South Seas behaves as one sustained wave train with powerful laterals and breaking shoulders. Button Hole (Rapid 18) contains the signature feature within the sequence.
The water
Character: continuous wave train (high water) / stepped pool-drop (moderate water).
Features: four distinct rapids in quick succession (Rapids 16–19); Button Hole feature at Rapid 18; irregular, choppy wave patterns at high water; transition into Ben Hurt (Rapid 20) at the bottom.
Hazards: limited recovery water at high flow; Button Hole lateral at Rapid 18; sustained wave action leads directly into Ben Hurt and Big Drop 1 downstream.
How it changes with flow
Low water: Rapids 16–19 run as separate drops; South Seas as a named sequence is less pronounced.
Medium: Classic Mile-Long character — stepped wave trains with eddies between.
High water: The sequence coalesces into one continuous wave train — the 'South Seas' identity is most recognized at this flow.
Scouting
Groups generally do not scout South Seas itself — the Mile Long scout above Capsize (Rapid 15) covers the sequence visually. Button Hole is the feature worth spotting from upstream.