Joe’s PADI IDC and Divemaster classroom
To be a professional PADI instructor or Divemaster you need to know how to read environments and how to explain certain changes in conditions or have the answer to “Why can’t we dive here today as it looks perfect from the boat”. To be able to do so we need to understand what causes Water movements especially Tides, Waves and Currents. If you take your divemaster course or instructor course on Bali at Joe's Gone Diving, you will find this is great knowledge to have.
In this Blog, we are going to have a closer look on Tides in theory:
First and most important what causes tides? Low and High tides are caused by the gravitational pull of the moon and the sun on the ocean. Creating two water bulges, waves on opposite sides of the Earth.
As the sun and the Moon are changing relative positions the size of those bulges change. When they are aligned (Full moon) we have the highest and the lowest Tide because they are pulling together in one direction. If they cancel each there out to some degrees at the right angle there is less variation between high and low tide. As the Earth rotates the position of the bulges change, causing our daily high and low tide.
If, however the world would be covered in Water we would have two high and two low tides a Day. The reality however is that the range of tides varies. In general, some places close to the equator have less varies in tides other than areas at high and low latitudes have extreme differences.
In a practical approach, how does that affect our planning as dive professionals:
First, you need to know the time and size of high and low tides at the side. This is simply a matter of consulting different tables, a good link for Bali tides is http://www.indosurf.com.au/tide_charts.html. Generally speaking, the best time to dive is at high tide or during slack high tide which is the time between rising and ebbing tide.
When you then arrive at the dive site, evaluate conditions to see how the tide plus other variables are affecting current, visibility waves and so on. As for an example currents can combine with tides and make the flow even stronger than you would normally encounter.
Some locations are not affected by tides at all. The water might be higher or lower but other than that everything is the same. In that occasion, you don’t need to plan for tides at all.