how to anchor and place shot line

[Richard Mason]

Originally Posted by PW1664

Helen makes a good point; I infact wouldn't anchor or tie off the RHIB while divers are in the water;

Although the idea of the anchor to bouy and lazy line is a good one, for me it's a compromise, albeit a small one. I keep the boat running to ensure there's no chance of engine starting problems in case of an emergency pick up...

Keeping mobile also allows you to just stand off the bouy, keeping watch for traffic, enebling you to put yaurself between divers/bouy and any craft that ingnore your A flag as well as help position the RHIB if it's a bit choppy...

Horses for courses; it's common practice to anchor here - down this part of the world, we rarely have big tidal streams and our population density is so low so that even in the popular areas, we rarely see other boats, particularly close inshore to the cliffs where we do 80% of our dives.

This is today's tidal prediction for Hobart:

Tide Predictions for Tasmania

TIDE PREDICTIONS FOR HOBART
FEBRUARY - 2008
Tue 19 Wed 20 [Full Moon] Thu 21 Fri 22 Sat 23 Sun 24 Mon 25
Time Ht Time Ht Time Ht Time Ht Time Ht Time Ht Time Ht
0558 1.45 0652 1.41 0059 0.78 0229 0.76 0402 0.73 0518 0.67 0620 0.61
1334 0.22 1424 0.27 0745 1.33 0839 1.23 0944 1.12 1057 1.02 1202 0.96
2001 0.95 2045 0.96 1511 0.33 1555 0.41 1634 0.50 1708 0.60 1735 0.69
2352 0.79 2132 0.98 2218 1.02 2300 1.06 2335 1.10
Tasmanian Tide Tables Book and Tasmanian port information

We rarely get much more than a metre difference between successive high & low water, so in some ways, it's like being in a lake in many places, currents are very modest.

[ChristianG]

Originally Posted by Richard Mason

Lastly, first pair in should swim down the anchor line and check that the anchor is secure, not tangled with the chain and that the chain is laid out straight. It's also a good idea if the last divers out can loosen the anchor, and make sure it's not jammed under a rock/in a crevice or wreckage.

I devised, I'm sure I'm not the first one, a way of ensuring as best as humanly possible, a method of securing and unsecuring an anchor.

On the (private) dive boat that we used to (sob) dive from the anchor was usually set by me. Each diver then had a clip and wrist band (CWB) that they took with them and the first divers ensured that the anchor was properly set. All divers then clipped their CWBs to the top of the anchor chain and removed them on ascent, thus ensuring that the last divers "unsecured" the anchor (all other CWBs having been removed), in fact in appropriate circumstances actually let it drift in the sand if on a wreck.

Yes, that is local conditions not tidally affected but for our conditions it sure worked.

Except if someone got lost and did a blue water ascent, something that happened exceedingly rarely because that diver got it in the neck like you wouldn't believe. The culture on that boat was, you get lost, find your own bluddy way back (well, within reason).

[PW1664]

Originally Posted by Richard Mason

Horses for courses; it's common practice to anchor here - down this part of the world, we rarely have big tidal streams and our population density is so low so that even in the popular areas, we rarely see other boats, particularly close inshore to the cliffs where we do 80% of our dives.

This is today's tidal prediction for Hobart:

Tide Predictions for Tasmania

TIDE PREDICTIONS FOR HOBART
FEBRUARY - 2008
Tue 19 Wed 20 [Full Moon] Thu 21 Fri 22 Sat 23 Sun 24 Mon 25
Time Ht Time Ht Time Ht Time Ht Time Ht Time Ht Time Ht
0558 1.45 0652 1.41 0059 0.78 0229 0.76 0402 0.73 0518 0.67 0620 0.61
1334 0.22 1424 0.27 0745 1.33 0839 1.23 0944 1.12 1057 1.02 1202 0.96
2001 0.95 2045 0.96 1511 0.33 1555 0.41 1634 0.50 1708 0.60 1735 0.69
2352 0.79 2132 0.98 2218 1.02 2300 1.06 2335 1.10
Tasmanian Tide Tables Book and Tasmanian port information

We rarely get much more than a metre difference between successive high & low water, so in some ways, it's like being in a lake in many places, currents are very modest.

A good point and well made....

[marine521]

I dont know if this helps but I thought that I should post this link here
Good Shot - DIVE Skills & Thrills

R.

[searider]

thanks marine521 for that web page as all info i got im taking on board and learning new ideas

[scuba steve irl]

our club never drops ancor before droping the shot . shot line should be slightly longer than the required depth have a heavy but not to heavy weight and a lagrge bouy to stop divers pulling it under .

[Peetoki]

Just a couple of points. First of all, yes it's a good idea to be able to unclip the anchor line from the boat so you can pick up divers, etc., but PLEASE have a spare anchor and line on the boat! And the best anchor for stopping a boat drifting may not be the best for dropping into a wreck (plough for sandy bottom, grapnel for the wreck was my preference - decide on your own, but at least think about it). I know of situations (not me, honest) where boats have unclipped from the anchor line and then had engine trouble...

My second point is that when dropping a shot, you need to make sure it dosn't tangle on the way down. Even if it untangles itself as it drops, that can delay it so it misses the "target" as it drifts past in the tide. I like to have two guys dropping it, one either side of the stern, one holding the shot and the other holding the buoy. They then pay out the line behind the boat as it motors uptide towards the drop area, so it floats in a big arc, well clear of the prop, of course.
When the cox shouts to say they should drop the shot, they throw both shot and buoy overboard behind the boat. The shot will go down quickly, with almost no drag, as the line can't snag, and the buoy is not pulling through the water. Don't know if I've described this very well - but it works well in practice!

[fibrefab2]

Horses for courses; it's common practice to anchor here - down this part of the world, we rarely have big tidal streams.

We rarely get much more than a metre difference between successive high & low water, so in some ways, it's like being in a lake in many places, currents are very modest.

Pretty much the same over here in WA.
As there is nobody left on the boat when we dive , I usually drop the main anchor (SARCA = sand and reef combined anchor) with 10metres of chain and is painted white so its easy to spot! off the front and when thats dug in I chuck a reef anchor (grapnel) with 5 metres of chain off the back in case the wind swings around or the main anchor lets go. Always check both anchors before and after main dive.
I also deploy a "mermaid line" off the back in case I miss the boat on the way up.
I'm not a fan of the folding grapnels as they can close up when you least need it, I use the bendable type that will hold your boat, but will pull out when you give the throttle "some herbs"

Some of the dive charters use a dive marker/shot line to mark the dive location as they motor over the dive site and then swing around and anchor on the same spot (?????????)

IMO I'd drop a marker on the dive site / wreck. Swing in and drop divers back on the shotline and then stand off, till divers surface (under a dsmb if they've missed the shot.) Last diver off the bottom to ensure shot is free to be retreived.