Substantial reef damage from boat anchor... again

[gcarter]

I do not believe for a second that all of that was caused by this one anchor incident.

 

[Zeagle Eagle]

I don't think all that "damage" was caused by an anchor chain. I think something else has happened.

 

[mmmbelows]

In the video where is the undamaged part of the reef? I can't tell where the damage starts or stops, the area looks like it's been dead for a very long time. Looks like they dragged an anchor through an old dead reef. I've dived sites that were recently dramatically damaged and what's missing from that video are the surviving bits of the reef that remain untouched and most significantly all the damaged coral, tubes fans etc, that ends up on the bottom in terrible piles of evidence of the destruction.

 

[Ambassador Divers]

I have personally been diving this area 2-3 times a month for the past 18 years, this damage was indeed caused by Tatoosh. For those who think that the condition of this site is normal or somehow typical of diving Grand Cayman, please contact me. I'll be happy to show you otherwise

 

[Ambassador Divers]

There doesn't appear to be any discernible demarcation between the damage area and what might have been considered healthy area. If the reef had been recently damaged, wouldn't there be small areas of live growth and broken pieces of live growth strewn about? The entire area looks as if it has been unhealthy/dead for quite a while. Just my observation from the video.

The video only highlights the damaged area. The entire area is dead/smashed. Most of the coral structure is broken an overturned. I looks eerily like the George Town harbor anchorage site. The reef surrounding the damaged area is healthy "relatively speaking". We have, like every other warm water diving destination, seen massive live coral coverage decimation over the last 30 years due to ocean acidity, coral bleaching and over fishing.

 

[mmmbelows]

Weird. It's hard for the layman to understand what they are seeing. Is there anyway to show where all the live stuff ended up? Where is all the healthy stuff that existed prior to the damage? This is what I've typically seen...

 

[Insta-Gator]

We purchased a timeshare in GC more than 20 years ago. For most of that we visited/dived GC annually. Yes, it is getting worse, all around the island. But not just GC. As mmmbelows indicated, there is usually a more dramatic visual between chain damage and pre-damage areas. Anyway, I hope all the GC reefs rebound soon.

 

[Itsacon]

I guess I don't understand enough about how boat anchors work. Why do they have such a long chain on the sucker such that it was even possible to touch 14,000 sf of any kind of bottom?

In the article they explain that the ship dropped anchor at a designate (sandy) place, but the anchor got pulled loose, and dragged across the reef, doing the damage pictured.

Whether it's the owner's fault, the crew's fault or Poseidon's fault is a debate I'm not getting into.

 

[Wookie]

according to the article, it is "mitch miller's reef". They also have some photos from October 2015 Mitch Miller's Reef | Scuba Diving in West Bay | iDive Cayman

I guess I don't understand enough about how boat anchors work. Why do they have such a long chain on the sucker such that it was even possible to touch 14,000 sf of any kind of bottom?

Think about it. 14,000 square feet is an area 140' x 100'. On any day I anchor in good holding ground, I will lay out 3-400' of rode in 50 feet of water. Spree is 100 feet long. Tattoosh is 300 and something feet long, so they probably lay out an equivalent rode in chain . 3/4" stud link, maybe 1" stud link. The day after they anchored, a norther came through, which would have shifted Tattoosh on her anchor and spun her around. I can easily see this kind of damage. I think 14,000 square feet is even a small estimate.

How do boat anchors work? Well, they work by adding tons of weight to the bottom, and making it difficult for the wind to push against the hull. The Spree is pretty light, 70 or so tons displacement. We do not use a chain rode, we use rope for ease of handling, and because chain isn't necessary. As light as we are, we get pushed against the rope rode and it stretches, and we bounce back. A big steel hulled vessel displacing many hundreds of tons will get inertia up as it swings on the anchor, and it takes a lot of weight to slow down and stop the swing. The chain lays on the bottom and provides that weight. The more the chain is tangled up on the bottom (plowing through silt, mud, sand, and yes, coral), the less chain is needed to stop the swing. The anchor's job in this case, is to keep the chain from slithering off in the sand. The anchor "anchors" the end of the chain. It's the chain that does all of the work.

 

[CuzzA]

according to the article, it is "mitch miller's reef". They also have some photos from October 2015 Mitch Miller's Reef | Scuba Diving in West Bay | iDive Cayman

I guess I don't understand enough about how boat anchors work. Why do they have such a long chain on the sucker such that it was even possible to touch 14,000 sf of any kind of bottom?

Contrary to what many would think, it's the weight and length of the chain laying across the bottom that keeps a vessel in place, not the actual anchor itself.

If a vessel didn't have a chain on the anchor line every time the vessel was raised by the crest of a wave the anchor would be picked up and moved.

People are often shocked when they buy a boat and find they need an anchor chain 2, 3, 4 times the length of their vessel, depending on the depths they intend to anchor at.