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January 6th 2014

05 Jan 2014 ="post-tag" > Written by  ="post-tag" >

You see?
good-visAll I can say is wow. After around 2 months of monsoon diving with reduced visibility, I took my open water students on dives 3 and 4 of their course this morning, and the "vis" was fantastic- 15 metres, and fish everywhere. Dive sites twins and white rock we're equally beautiful, and Chumphon pinnacle was also amazing according to our fun divers. It was a great reminder of what conditions are normally like on Koh Tao, and I look forward to teaching a lot more courses throughout the year with similar or even better conditions.
But why does visibility vary? Like life, it's complicated and has to do with loads of things. The latitude of the dive site, and the time of day will both affect how much light enters the water instead of being reflected off the surface- generally the closer to the equator a dive site is, the better the visibility will be (so contrary to popular opinion, noon is actually the best time to dive if you want good vis, but there is usually more marine life to see in the mornings). The action of waves, tides, and currents also stir up the bottom and suspend particles in the water, which scatters light in all directions (Rayleigh scattering for the geeks), and guess what- reducing vis!
The type of bottom can also affect vis; disturbed sand or gravel will sink back to the seabed much quicker than clay or silt. Run-off from land inundates the water with sediment, which in turn may provide nutrients for algae to bloom and therefore reduce vis further (this also helps to explain why whalesharks tend to be more prevalent after heavy rain). Biological particulate matter can also reduce vis because they scatter more light, but they also enable filter feeding organisms to go on a feeding frenzy, which serves to improve vis. Finally, thermoclines (thermo= temperature, cline= gradient) and haloclines (halo=salt), can reduce vis because two bodies of water with different properties meet and mix. This reduces vis because the refractive index of the light traveling through the water is altered, but you knew that already didn't you...
This is obviously just a broad summary, the interaction of all of the above make predicting visibility pretty difficult. But we know from experience that the next 10 months are going to be consistently good, 10-30 metres. If you don't know what that's like, you'd better get your ass over here and come diving with us!

10 things you SHOULDN'T do after diving:
1- Fly within 24 hours of completing your last dive.
2- Heavy exercise- why would you do that at any time anyway?
3- Freediving. To the layperson, duck diving, no, that wasn't a typo of di....
4- Breathe laughing gas- it won't be as funny as you think.
5- Have a deep tissue massage. Give it at least a few hours you lazy aching masochist.
6- Write a blog for work.
7- Write a blog for fun.
8- Play in the road with your imaginary friend.
9- Think you can swim to Chumphon and decide to prove it.
10- Log the dive from the depth gauge of your SPG, that says you went to 80 metres.

10 things you SHOULD do after diving:
1- Go on trip advisor and say how amazing your instructor or divemaster was.
2- Go diving again, but with someone else- your divemaster wants the afternoon off.
3- Give the tizer or umbongo that you brought with you to your instructor or divemaster. 
4- Offer to write the Big Blue blog for your instructor.
5- Offer to pay your instructor for the privilege of writing the Big Blue blog for them.
6- Put a thousand baht behind the bar for your instructor.
7- Figure out why it's not called residential nitrogen when doing a repetitive dive. True story.
8- Realise that your way of remembering the pre-dive safety check is a bit weird- Bruised Wrists Reduces Arse Fun.
9- Revel in your weirdness and patent your method for remembering the pre-dive safety check.
10- Ask your instructor for a new battery for your LPI, as the one that powers your inflator must be dead, because it won't inflate after washing.

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Read 940 times Last modified on Tuesday, 24 October 2017 08:24

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