Dive 1 — Calibration and Practice Run (No Camera)

Safety and gas bind before the survey does. Adapt to the conditions or stop — a partial ring is always a valid outcome.

Dive 1 establishes the day's calibration — everything the survey needs, measured by counting kicks — and lets the team rehearse the survey pattern without the task load of operating a camera. No capture is made and nothing is counted on this dive. The camera is introduced on Dive 2, once calibration and team mechanics are reliable.

The reason for separating calibration from capture is that the entire survey geometry is computed from the calibration, and the relative index divides every count by the area the visibility sets (Appendix A.3). The calibration must be established before any data is collected, and a diver does better work establishing it when not also managing a camera. Dive 1 buys that focus.

Working in kick cycles. Underwater a diver cannot perceive absolute distance — only count kicks. So this survey's unit of length is the kick cycle (both legs once is one cycle — two kicks), and every distance below is a kick count. This matches what the diver can actually do and removes any need to convert to meters or feet in the water. (A kick cycle is not a fixed distance — it changes with fins, exposure suit, current, and fatigue — which is why the calibration is re-done every dive and why comparisons across dives use a ratio of kick counts; see Post-dive and Appendix A.7.)

Performance requirements. By the end of this dive the student will have:

1. Established the calibration count K — the kick cycles needed to swim the marked 30 m / 100 ft line at a normal, relaxed pace (the same line and distance used in the Advanced Open Water Underwater Navigation dive). This sets the day's kick as the unit of length.

2. Established the visibility r, in kick cycles — the kick count out to where the standard marker fades — by the two-Team marker-fade procedure, every diver within reach of a buddy (Module 2).

3. Derived the survey geometry from r: the swim-out R = 2r kicks and the six-station ring (below).

4. Rehearsed the survey movement — out 2r to the first center, then add 60° and swim 2r along each edge around the ring, holding a stable no-contact station at each center — and the photographer and recorder roles, all without a camera, swapping roles.

5. Recorded K, r, and R = 2r on the survey slate.

The survey geometry, computed from r. The survey is a ring of 360° panoramas around a center point. For the panorama disks (each of radius r) to sit tangent to one another, their centers must be 2r apart, which places them on a ring of radius R = 2r. Equal disks tangent around a ring at twice their own radius number exactly six — this is a fixed fact of the plane, the same "six circles fit around one" hexagonal arrangement (the 2D kissing number). So the pattern needs no choosing: out 2r kicks to the first center, then a panorama at each of six centers spaced 60° around the ring. Visibility r sets how far out the ring sits and how large each sample is; it never changes the count, which is always six. The full pattern — the edge headings and the perimeter walk — is given in Dive 2.

On "exactly six" in practice. Six is exact only when the diver swims R = 2r cleanly. In real water — current, trim, a kick count off by a fraction — the ring runs a little large or small, so the six disks overlap slightly or leave slim gaps rather than meet perfectly. This does not bias the survey: six is the nominal pattern the diver executes, the departures are small and random rather than systematic, and they wash out of the averaged density. Six is the geometric target, not a claim of perfect tangency.

Equipment for this dive. Standard scuba kit with a nitrox computer set to the analyzed mix; the marked calibration line (marked at fixed intervals, at least 30 m / 100 ft long) and the standard high-visibility marker; a compass; the survey slate. No camera is carried on this dive.

Pre-dive briefing. Confirm the Team configuration (Team A and Team B) and the rule that no diver is ever alone or beyond reach of a buddy — the calibration is performed by the Teams together on the marked line. Confirm the calibration-line layout and the kick-cycle definition (both legs once, Module 2), the gas plan, and the gas-limited turn-around. The marker-fade separation and the ring rehearsal run per the method as taught (Modules 2 and 4).

The dive.

1. Descend to the center (reference) point; establish neutral buoyancy and horizontal trim before anything else — an unstable diver cannot make a clean calibration or a clean count.

2. Calibration count K. Deploy the marked 30 m / 100 ft line. Swim it at a normal, relaxed pace, counting kick cycles. That count is K — the day's kick-length and the unit everything else is expressed in.

3. Visibility r. Team A holds the standard marker and stays put; Team B moves out along the line together — both divers within reach of each other — counting kick cycles until the marker can no longer be distinguished from the background; the first Team B diver to lose it calls the fade. The Teams hold visual contact throughout. That kick count is r, the visibility in kicks. (If the marker is still distinguishable at the line's end, visibility exceeds the line — record r as ≥ that count and extend the line if practical.)

4. Derive the geometry. Compute R = 2r kicks and confirm the six-station, 60°-spaced ring.

5. Practice run. Rehearse the survey pattern without shooting. From the hub, swim out 2r kicks on 000° to the first center and hold a stable, no-contact station (the panorama position); then add 60° to the compass, swim 2r along the edge to the next center, and hold — working around the ring through headings 120 / 180 / 240 / 300 / 000 / 060, the closing 060° leg returning to the first center. The pair moves as a unit (Module 6) and rehearses the photographer/recorder roles; swap roles and, gas allowing, run the ring again. The closing leg landing back on the first center is the navigation check. If at any point the count or the bearing is lost, do not guess — return toward the hub to re-reference, or end the run.

6. Ascend with a safety stop.

Post-dive. Record K, r, and R = 2r on the slate; these carry forward into the capture dives. Across dives, the density is expressed using the ratio r/K so the day's kick-length cancels and counts stay comparable even though a kick cycle is not a fixed distance (Appendix A.7). Debrief the calibration, the ring navigation (did the closing leg land back on the first center cleanly?), buoyancy, and station-keeping. Weak buoyancy or navigation is remediated before the camera is added on Dive 2.

Assessment. The dive is satisfactory when the student has produced a defensible K and r, derived R = 2r and the six-station ring, walked the ring closing back onto the first center within a reasonable tolerance (consistent with the Advanced Open Water return tolerances of roughly 6–15 m over the distances swum), and held a stable, no-contact station while correctly rehearsing the two team roles.

Depth range. 6–18 m, at a depth representative of where the survey will run.