Soundings
The following are extracts from the daily survey log of the R/V Ellen Strand, a 22-meter hydrographic vessel contracted to remap the floor of Garron Sound ahead of a proposed cable crossing. Entries are by the survey lead unless noted. Technical tables have been omitted.
Day 1. Arrived Garron Sound 1420. Weather fair, swell negligible, sound is well sheltered. Anchored in the lee of Skerry Head in 31 m. Calibrated the multibeam (patch test good), ran a sound-velocity cast, began the first survey lines at 1610.
Existing charts are from an Admiralty survey in 1911, lead-line soundings, not much else. Expect a glacial basin: a flat mud floor at 55–62 m with a sill at the mouth. Ran six lines before dark. Floor exactly as expected. Flat as a table. Nice to have a boring one.
Crew: myself, Hal Brodie (master), Tomasz (engineer), Neve (data processor), Callum (deckhand/cook).
Day 2. Full day on the lines, north to south, 50 m spacing. Floor 58–61 m throughout. Neve processing overnight.
Day 3. Neve flagged an artifact in the overnight data. Line 14, about 800 m southwest of the anchorage: a rectangular feature roughly 40 m by 12 m, raised 1.2 m above the surrounding floor, with very straight edges. She thinks it’s a processing error, a bad patch of sound velocity. I think it’s probably a wreck, or a dumped barge. Re-ran line 14 in the afternoon. The feature is there. It’s not a barge. Barges don’t have edges that clean.
Logged it as an obstruction for the cable people.
Day 4. Re-ran 13 through 15 to get a better picture of the obstruction.
There are two now.
The first rectangle, as before. Directly northeast of it, toward us, a second one: same footprint, 40 by 12, sitting on top of the first and offset from it by about 10 m. Raised a further 1.2 m. A step.
Neve checked the timestamps. Line 15 on Day 2 crossed exactly where the second step is. Day 2 shows flat mud.
Brodie says the sound is known for slumping, that mud moves. I’ve seen mud move. It doesn’t move into right angles.
Day 5. Three steps. Same offset, same height. The third is 780 m from the anchorage, give or take, and on the same bearing. The bearing points at us.
Ran a camera drop at the base of the first step. Visibility poor, the usual brown snow of a mud basin. The camera touched down on the lower floor, and in front of it, filling the frame, was a wall. Pale, smooth, vertical. Not rock. Not metal either. Neve thought it looked like bone. I think it looked like nothing at all; it looked like the camera had been pressed against a blank sheet. We lifted the camera and lowered it again three meters onto the top of the step, and the surface there was the same, perfectly level, and very lightly dusted with silt, the way a floor gets in a house nobody’s lived in.
We have the footage. I’ve watched it a dozen times. I keep thinking that it looks swept.
Day 6. Four steps. Five steps. It added two overnight.
I’ve emailed the office. Told them we have an unexplained, apparently growing feature, that it may be geological and it may be something else, and asked for guidance. Have not yet heard back.
Tomasz asked if we should move the anchorage. Brodie said no; we’re sheltered here, and the forecast is deteriorating, and the thing is the better part of a kilometer away. Tomasz said, “It was.”
Day 7. Seven steps. Each one exactly 1.2 m up and 10 m closer. The top step is now at 50 m depth and 730 m from our position, and our position has not changed. Brodie has had the anchor watch logged hourly, and we have not dragged a centimeter.
Callum asked what happens when it reaches the surface. Neve did the arithmetic for him on the whiteboard in the galley, in front of everyone, because she’s like that. Fifty meters at 1.2 a step. Forty-two steps. Seven hundred and thirty meters at ten a step. Seventy-three steps.
Callum said, “So it gets to us first.”
Neve said, “It gets under us first.” Then she rubbed out the whiteboard.
Day 8. No reply from the office. Satellite link is working; our messages are going out. Nothing is coming in.
Eleven steps. They’re arriving faster.
I’ve run the multibeam over them in every direction, in case it’s a refraction effect, an inversion layer, anything. It isn’t. The data are clean. The steps are not quite as wide as I’d thought: the top surfaces narrow very slightly as they climb. Like a stair on a curve. Like a stair coming up out of a basement.
Day 9. Weather in. Gale from the southwest. We stayed at anchor. Couldn’t survey in this sea, and I’ll be honest, nobody wanted to. We could hear it on the hull, though. Not knocking. A kind of long, regular pressure, every few minutes, as if something below had set down a great weight and stepped up onto it.
Neve kept the multibeam logging from the anchorage, pointed straight down. It’s a narrow swath at this depth, but it covers what’s under us.
Day 10. Calm. Callum and I took the tender out to the feature at 0700 with the portable sounder.
There is no longer any feature at 700 m. The floor there is flat mud again, 59 m, as it was in 1911. All the steps are gone, as if they’d been taken up and carried away.
Neve went quiet and then went down to look at the data from the anchorage. I followed her. The swath under the hull shows the floor at 31 m the whole night through, as it should. Then at 0412 it shows 24. At 0419, 18. Then 11, then 7.
The last value logged was at 0446. It’s 2.4 m, which is our draft. The top step is under the keel.
We have not dragged. We are riding perfectly level. I’ve never known a boat to sit this still.
Day 10, 1130. Brodie wants to cut the anchor and run. Tomasz says the engine turns over but the shaft won’t. Something is holding the screw. It isn’t fouled. Tomasz says it’s being held, the way you’d hold a child’s wrist so they don’t touch the stove.
The sounder under us now reads the same as the depth of the hull. We’re not floating on water at all. We’re standing on the top step. I keep thinking about a floor that’s been swept for guests.
Callum just came up from the galley and said there’s somebody knocking on the bottom of the boat. Not knocking, he said. Waiting. Like the polite part before you open the door.
Addendum, filed by the operating company:
The Ellen Strand was located at anchor in Garron Sound on Day 14 by the coastguard, after the company failed to re-establish communications. The vessel was undamaged, its engine and shaft in working order, its anchor holding in 31 m of water. No crew were aboard. The survey log was found open on the chart table. The last entry is reproduced above.
A survey of the sound conducted by a second contractor in the following month found a flat mud floor at 55–62 m, consistent with the 1911 Admiralty chart. No obstructions were found. The cable crossing was approved and laid without incident.
The second contractor’s survey lead did ask that one detail be placed on record. On her final line, directly beneath the Ellen Strand’s anchorage, the multibeam returned a single shallow sounding, a point no larger than a doormat, at a depth of 2.4 meters, which on repeated passes she was unable to find again.