Watersport Beach to Bali Hai beach

Setting

• The Watersport Beach to Bali Hai beach transect is the longest of the Necker Island snorkel routes, a roughly 1,811 m swim along the island's leeward shore from the watersport beach to Bali Hai beach.
• The 51 frames from this transect are unevenly distributed along that route, consistent with Anderson's field note that he did not take many photographs until near the watersport center.

Benthos

• The reef bottom documented in the remaining 37 frames is a shallow, low-to-moderate relief hard-bottom and rubble pavement, colonized largely by turf algae and coralline crust, with sand channels and patches throughout and scattered live coral colonies rather than continuous coral framework.
• Octocorals — sea plumes, sea rods, and sea fans — are a consistent presence across the transect (e.g., Image 14, Image 34, Image 35, Image 40, Image 42), often more conspicuous in a given frame than any stony coral.
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• Stony coral is dominated by small to medium brain-type colonies (Diploria/Pseudodiploria-complex) (e.g., Image 10, Image 12, Image 13, Image 32, Image 33, Image 45) and by Acropora palmata-type elkhorn or plate colonies, most of them live (e.g., Image 22, Image 31, Image 39, Image 43, Image 44, Image 46) but in one area extensively dead (e.g., Image 15).
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• Boulder-type mounding coral (Siderastrea/Porites-complex, hedged) forms denser patches of cover in a couple of frames (e.g., Image 19, Image 20).
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Along the transect

• The earliest usable benthic frames, taken close to the watersport beach, show a sparse sand-and-rubble bottom with almost no live coral — a lone sponge or tunicate on sand (e.g., Image 2) — and the first coral colony of the transect, a brain coral, does not appear until (e.g., Image 10), after eight consecutive topside frames documenting the beach launch.
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• Coverage becomes steadily denser and more consistent once the route nears the watersport center, as Anderson's field note anticipated: frames (e.g., Image 11, Image 12, Image 13, Image 14, Image 15, Image 16, Image 17, Image 18, Image 19, Image 20) show a mix of small coral clusters, octocoral stands, a patch of dead branching coral skeleton (e.g., Image 15), and the first dense boulder-coral surface of the transect (e.g., Image 19, Image 20).
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• The middle stretch (e.g., Image 21, Image 22, Image 23, Image 24, Image 25, Image 26, Image 27, Image 28, Image 29, Image 30, Image 31, Image 32, Image 33, Image 34, Image 35, Image 36, Image 37, Image 38, Image 39, Image 40) is the most heavily photographed section and shows the most texture change along the route, alternating between near-bare hard-bottom pavement (e.g., Image 21, Image 23, Image 29, Image 30, Image 36), a locally dense branching-coral patch (e.g., Image 27), isolated brain coral colonies sitting on open sand (e.g., Image 33, Image 37, Image 45), and several live elkhorn or plate colonies of modest size (e.g., Image 22, Image 31, Image 39).
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• The final benthic frames before the transect reaches Bali Hai beach (e.g., Image 41, Image 42, Image 43, Image 44, Image 45, Image 46) include some of the healthiest-looking individual colonies of the transect — three live elkhorn or plate corals with intact growing edges and no visible bleaching (e.g., Image 43, Image 44, Image 46) — immediately followed by the shoreline and beach photographs that mark the end of the route (e.g., Image 47, Image 48, Image 49, Image 50, Image 51).
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Condition

• Mortality is visible but localized rather than reef-wide: a substantial stand of dead branching coral skeleton, colonized by turf and interspersed with living octocorals, appears at (e.g., Image 15), and a large boulder-type colony that reads as mostly dead and algae-covered appears at (e.g., Image 26).
• Elsewhere, dead coralline pavement and rubble make up much of the hard-bottom matrix, but the live colonies photographed — brain corals, elkhorn or plate corals, and boulder corals alike — show intact tissue and clean growing margins, with no bleaching or disease apparent in any frame.
• No macroalgae overgrowth beyond routine turf cover was noted on any live coral surface.
• No corallivores evident.

% cover

• CoralSCOP's mask-sum photographic index puts coral cover for this site at 12.3% across the 51 frames (sd 9.7), consistent with the pattern visible in the frames themselves — a reef where live coral is real but patchy, set within a hard-bottom and octocoral matrix rather than continuous coral cover.
• That figure should be read as an upper bound: it is a mask-sum photographic index, not a diver survey, and it runs high against manual point counts on Anderson's own same-image tests (-4.1 to +27.8 pp, mean +7.5 pp).
• At Necker's Red Dock site, 31 manually annotated frames gave 7.8% hard coral against CoralSCOP's 16.8% on the same images — roughly double — so the true hard coral cover along this transect is likely well below the reported 12.3% figure.