The Singapore Strait is a complex body of water with narrow passages between little islands and large bodies of water to the East (South China Sea) and to the NW (Indian Ocean via the Malacca Strait). Additionally, Singapore is about where 2 different tidal flows merge and to boot…these tidal flows are driven by monsoonal wind patterns. I don’t know all the technical “lingo” to go into depth..let’s just say it’s important to know if the tidal flows are against you, how far you have to go, and where are you going to cross the Strait (traffic of course).
With only 46 miles to get from Indonesia, Batam Island (Nongsa Point Marina) and across the Singapore straits and then up the river to Johor Malaysia, we needed to time of our passage so that we could utilize the west setting currents (up to 4 knots) that happen during a rising tide …otherwise we would have this current going against us and would possibly not make the 46 miles in one day. Lucky again…the tide was headed our way but we had to leave at the crack of dawn (5:30 am).
This is not what the tide did for our trip but to give you an example of what could go right/wrong. The current is heading East to West, I believe currents flow in this direction on an rising/incoming tide. This chart show the flow the strongest (RED color) right where we are at about 4 knots rate of flow. You can image if we were headed the opposite way, we could literally be going backwards! 
Another important point is our vessel is not “checked into” Singapore, therefore we needed to stay OUT of Singaporian waters…we literally heard the Harbour Port Control hail our friends as they crossed over “the line” rounding a corner so we made sure to be out in International Waters, just outside the shipping lanes! 
In theory, the cargo ships are supposed to “slow down” at the “blank” white “crossing zones”. In practice…they don;t care and it’s your responsibility to get out of their way. When they are moving at 15-20+ knots speed over ground, it’s like playing Frogger. We choose to cross as far West so we can stay in Indonesian/International waters for as long as possible. Then we just went for it!
We found an almost perfect break between cargo ships and throttle down! We passed all kinds of ships: Red ones, black ones, blue ones, ones with cranes, some with tanks, it was like the Dr. Seuss book “One Fish, Two Fish, Red Fish, Blue Fish” book but instead of fish…it was ships!
Still hugging the Singapore coast, we turned right to head up to Johor, Malaysia. We knew there was a bridge to go under and we actually heard some large and tall masted catamaran was hard pressed to go under and needed to wait until low tide to go under. Supposed to be 25 meters tall, plenty of space for our mast at 17 meter tall, it’s always nerve racking to go under a bridge…see the below video…
For those crossing in the future…here is a great tool and what we used to find out current strength and timing of currents to cross the Singapore strait.
Visit website and click on “Digital Tidal Atlas” 
Select between the 2 “anchorages” they provide. Sudong is the most West anchorage. The Eastern anchorage is near the South China Sea. 
Click “Accept” 
Select the date you are looking for…and a time though later you can see anytime you want…Click Submit… 
This is what you get…the colors of the arrows tell you the rate of flow to expect…. 
You can see there are different times at the bottom of the page and you can just click on it and see different rates of flow through out the date you selected. 
Other option (I am a visual person so I like to see it the arrows and colors) is to get an excel spreadsheet of rate and direction of flow. Not sure which is point A vs. B but they have Lat and Long so you can figure it out. 
Here is the output of Point A in excel form.
You can cross reference these rates of flow with High and Low tides from the below Singapore tides…
https://www.nea.gov.sg/weather/tide-timings
We crossed with no issues, though at times it was a bit hectic anticipating cargo ships on AIS and the fishing activity up the river to Johor, but other than that…We were in Malaysia..ready for another adventure : )
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