Dominant  Percentage   Percent  Class of 
System[1] Zone[2] Substrate[3] of Substrate Cover[4] Coral Cover[5] Relief[6]
basalt island[7] intertidal [8] UNCONSOLIDATED[9] none seagrass[10] none 1
sea stack[11] lagoon[12]      mud[13] sparse[14] macroalgae[15] sparse[16] 2
carbonate island[17] reef flat[18]      sand[19] moderate[20] non-coral Cnidarians[21] moderate[22] 3
closed atoll[23] back reef[24]   dense[25] crustose coralline algae[26] dense[27] 4
open atoll[28] reef crest[29]   continuous[30] encrusting coral or algae[31] continuous[32] 5
submerged bank/reef[33] fore reef[34] HARDBOTTOM[35] percentages[36] emergent vegetation[37] 25%[38]
continental reef[39] shelf[40]      rubble[41]   coral[42]  
  escarpment[43]     rock[44]      
  land[45]      man-made structure[46]      
           
           
unclassified[47] unclassified[48] unclassified[49] unclassified[50] unclassified[51] unclassified[52] unclassified[53]
[1]
The "system" category includes the the largest scale of interest here and encompasses entire coral reef ecosystems.
[2]
The "Zones" category includes some indication of the location of the feature relative to the shoreline and open ocean, and may include a description of seafloor shape as well.

[3]
The "Substrate Composition" category indicates the dominant type of substrate, which may or may not be covered by coral, macroalgae, thin layers of sediment, etc. For unconsolidated substrates, the grain size range is indicated according to a modified version of the Wentworth scale.  Note that rubble and boulder-size fragments are included under the "hardbottom" category, as growth of benthic colonizers may make it hard to distinguish between them and solid rock. Colonizers such as algae and corals are less likely to occur on sandy or muddy substrates .
[4]
The  cover" category quantifies  the occurance of macroscopic organisms growing on and attached to the sea floor. Quantities listed are the total percentage of seafloor that the organism covers. They may be expressed as measured percentages, or  binned into the following groups:

0% = none;
0> to <= 10% = sparse;
>10 to <= 50% = moderate
 >50% to <= 90% = dense;
>90% = continuous

The organisms listed here include those that have been observed colonizing the seafloor in Pacific coral reef ecosystems. Other organisms may be included as they are encountered.

Turf algae covers most hard substrate not otherwise colonized in these ecosystems. Too small to be readily identified in most benthic photographs, it is not included in this listing.

It is  not be practical to  include rarely observed species in these gereral-purpose maps, and it is recommended that entries in this category be limited to more commonly-encountered benthic colonizers.  The occurrence of rare species can be recorded in data layers designed for that purpose.
[5]
This column is included to ensure that there is a means for recording the presence of living corals in areas where they are not the dominant benthic cover. Otherwise, in the primary and other "cover" categories, corals are likely to be under represented. Their importance however dictates that their presence be indicated.  Values can be recorded either by general categories (e.g., sparse (<10% cover),  moderate (10 - 50% cover), and dense (>50%) cover that can be easily estimated from oblique photos, or by more specific percentages, (e.g. 45%), measured from vertical photographs, diver surveys, etc.
[6]
Relief class referes to the changes in vertical relief that best characterize an area. These may be measured in a variety of ways and are one way to express  rugosity.

Class     Relief (m)
  1                 <= 0.5
  2               >0.5, < 1
  3              >1, <=2
  4              >2, <=3
  5              >3
[7]
An island of volcanic origin and in which volcanic material is still subaerially visible.
[8]
That portion of the substrate that is both subaerially exposed and underwater during some portion of a normal lunar tidal cycle.
[9]
Unconsolidated sediments are defined here as being composed of predominantly sand-size or smaller (<2 mm mean diameter) grains. It may be hard, without actualy moving material around on the seafloor, to distinguish between rubble or boulders or solid rock. Rubble and boulders may also be covered by benthic algae or other colonizing organisms, further conplicating their differentiation. Accordingly, they are included here within the "hardbottom" category.  Sand-sized or smaller sediments, on the other hand, are relatively mobile  and tend to preclude the settlement and growth of many benthic colonizing organisms, making them easier to distinguish from rubble, boulders, and solid rock.
[10]
The percentage of live seagrass visible on the surface of the seafloor.
[11]
A steep-sided, mostly barren, rock island formed by the eroded remnants of a larger formation, e.g., La Perouse Pinnacle, Necker Island, and Gardner Pinnacles.
[12]
A shallow body of water near but separated from the open ocean by a barrier reef or other structure.*
[13]
Sediment with a grain size of < 1/16 mm.
[14]
Some live coral, but covering <10% of the substrate.
[15]
The percentage of macroalgal growth that is large enough to be readily visible to a diver a few meters above the seafloor. This category excludes low turf algae, which colonize most hard substrates that are not otherwise colonized, but are too small to be seen in many optical and diver-based surveys.
[16]
Some live coral, but covering <10% of the substrate.
[17]
An island composed of carbonate reef and detrital material without any volcanic structure,  and typically of low elevation.
[18]
Flat and shallow (typically depths less than a few meters) areas shoreward of a reef and characterized by coarse rubble, algae and sand.**
[19]
Unconsolidated sediment composed predominantely of grains with a mean diameter between  of ≥ 1/16 mm  and < 2 mm.
[20]
Living corals cover >= 10% of the substrate but <50%.
[21]
The percentage of non-coral Cnidarians, including hydrocorals, hydroids, soft corals, sea fans, sea pens, anemones, and black corals.
[22]
Living corals cover >= 10% of the substrate but <50%.
[23]
A ring-shaped coral reef that surrounds a lagoon, is surrounded by the open sea, and contains one or more passages.
[24]
The area between a reef and the shoreline, especially that portion of a reef structure inhabited by reef-building organisms and landward of the reef crest. In a barrier reef setting the landward boundary of the back reef is the seaward edge of the lagoon floor. In a fringing reef environment, the landward edge of the back reef (if present at all) may be marked by a shift from heavy colonization by reef building organisms to a  zone of sparse colonization of the reef flat.* ** ***
[25]
Living corals cover > 50% to <= 90% of the substrate.
[26]
The percentage of seafloor covered by living crustose coralline algae.
[27]
Living corals cover > 50% to <= 90% of the substrate.
[28]
An atoll in which much of the perimeter reef is absent.
[29]
A band or line that is typically parallel to the shoreline and represents the highest elevations of a fringing or barrier reef. The reef crest is often near mean sea level and may be subaerially exposed at low tide.
[30]
Living corals cover >90% of the substrate.
[31]
The percentage of seafloor covered by encrusting corals or coralline algae, for situations in which they cannot be differentiated.
[32]
Living corals cover >90% of the substrate.
[33]
A raised portion of the sea floor occurring at shallow depth but below the intertidal zone.*
[34]
The upper part of the outer or seaward slope of a reef, extending from the reef crest or seaward edge of the reef flat down to an area with a reduced slope marking the start of a shelf, or the point at which abundant growth of coral and coralline algae is restricted due to light limitation.* ***
[35]
Hard, consolidated substrate. Note that rubble and boulder categories are typically classified as large-grained sediments. However, they may be covered by algae, corals or other benthic colonizers and therefore indistinguishable from consolidated rock Accordingly, they are included within the hardbottom sub-category.
[36]
Living corals cover (for example) 25% of the substrate.
[37]
The percentage of the seafloor covered by vegetation, such as mangrove, that is located seaward of the low tide line but is also subaerially exposed.
[38]
Living corals cover (for example) 25% of the substrate.
[39]
A coral reef ecosystem located adjacent to a continental land mass.
[40]
A generally flat,  benchlike,  projecting ledge of rock.*
[41]
Fragments of coral or other carbonate reef material, typically of cobble size but with finer and coarser sediments mixed in.
[42]
The percentage of live coral covering the seafloor. These data are broken out as a separate layer as well.
[43]
The edge of a bank, island, or shelf where depths increase rapidly into deep oceanic water.***
[44]
Consolidated, hard substrate or boulders   (fragments with a mean diameter ≥ 256 mm) composed of any type of volcanic or carbonate rock.
[45]
Any portion of the substrate at an elevation above the intertidal zone.
[46]
     Most hard benthic substrates in the photic zone and not otherwise colonized will rapidly become colonized by turf algae.  However, very often turf algal communities are often too small to be distinguishable, in which case the substrate type is listed.
     As with sediments, man-made structures may be listed under "Substrate Composition" and may also be appropriate "Cover" category entries.
[47]
A particular data entry may be unclassified because image quality was poor, because not enough of an area was seen to classify, etc.
[48]
A particular data entry may be unclassified because image quality was poor, because not enough of an area was seen to classify, etc.
[49]
A particular data entry may be unclassified because image quality was poor, because not enough of an area was seen to classify, etc.
[50]
A particular data entry may be unclassified because image quality was poor, because not enough of an area was seen to classify, etc.
[51]
A particular data entry may be unclassified because image quality was poor, because not enough of an area was seen to classify, etc.
[52]
A particular data entry may be unclassified because image quality was poor, because not enough of an area was seen to classify, etc.
[53]
A particular data entry may be unclassified because image quality was poor, because not enough of an area was seen to classify, etc.