Summary:
There was a water color and underwater visibility change in version 1.16.230.54:
Underwater visibility has been improved
Underwater color has been tuned to better match Java Edition with a richer blue tint
But in version 1.16.230.56, alas, the color is again as it was before version 1.16.230.54 (blue) 😞.
The underwater visibility also changed to the old one (as before 1.16.230.54) with a color change that made it difficult to navigate the underwater caves.
Steps to reproduce:
Go into the water (preferably at sea).
Look at the color and underwater visibility of the water.
Observed results:
The color and underwater visibility of the water is not the same as in version 1.16.230.54
Expected results:
Water color and underwater is the same as in version 1.16.230.54 or as in Java
Notes:
One water fix was written in the 1.17.10.21 beta changelog:
Underwater fog is once again dependent on biome (MCPE-124266)
But this change was not supposed to affect the default water color and underwater visibility, but in fact, after this version, the water color and underwater visibility became the same as before version 1.16.230.54.
With decreasing altitude, the fog becomes very strong (not visible far). Because of this, it is impossible to move around in the underwater caves.
Image:
Underwater visibility in underwater caves
1.16.230.54
[media]
Java/Bedrock
[media][media][media]Linked issues
is duplicated by
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Comments

It was temporarily disabled.

This is intended because bedrock have different water by biome instead of the temperature, and it wasn't changing before, so now is fixed
@unknown
Alas, deleting one is not a solution for the other)
Moreover, in the list of changes, you can report that everything was returned due to errors.

I have made a water room in a geode with a conduit and I can't even see the prismarine layout fully. This is clearly a degrade in play, we now have 6 blocks of vision with a CONDUIT.


According to my experiments, it is the fog at depth that greatly reduces visibility. It also doesn't match the java version:
[media]java

To put some numbers on the visibility issue:
The max view distance in water is set by biome fog json files in in the vanilla behavior pack. The max distances have not changed since 1.16.100 (determined from looking at the installed game files on PC, not the sample pack). So the changes in 1.17.10 must have only been to how the fog data is processed.
The fog jsons set the maximum view distance in water as follows:
Oceans: 60
Beaches: 60, 50, or 15 depending on variant
Rivers: 20 or 30 depending on variant
Swamps: 8
All other biomes: 15
Testing in-game in 1.17.11 Hotfix I find that the actual max visibility in oceans is only 45 blocks. In other biomes the maxes are accurate.
Compared to Java, however, the visibility is horrible. In Java in a forest biome I can see the shape of blocks at least 80 blocks away. That may be a bug in Java, because the visibility with night vision is much less (MC-223256).

I don't understand how I can have 6 blocks of vision underwater in a desert biome if it is set to 15. Night vision, conduits, no changes. When i walk back 6 blocks the blocks in front of me become invisible.

In 1.18.0 the maximum view distance in water for every biome except swamp has been set to 60. Swamp is set to 30. So in most places the visibility is now much better than it was in 1.17.
Visibility also scales down below 0 Y, all the way to 1/3 of the base value near -64 Y. So in swamps it's 10 at world bottom, and in other biomes it's 20. Fortunately that's still better than it was in most places above even above 0 Y in 1.17. I think the scaling below 0 Y is intentional and should not be considered part of this bug.
Based on information cited in wikipedia, 60 is a realistic average visibility for ocean water: https://en.wikipedia.org/wiki/Underwater_vision#Measurement_of_visibility
@unknown: Thank you) I will test the visibility later. But I want to remind about the color of water, which is different from java color.

Murkiness has gotten significantly worse on Switch.
In 1.18.33, I can see an underwater lapis lazuli ore 10+ blocks away from submerging 1 block deep.
1.19.1, the ore is completely hidden unless I'm <5 blocks away, about 5 blocks from the surface.
Edit: This is a river biome near a plains village.

Murkiness in water seems much worse since I last played, at least a few weeks before 1.19. The 'fog' only let's you see a couple of blocks in front of you when you first enter the water and then it 'thins out' a little letting you see about 20-30 blocks before the blue wall of impenetrable fog stops you, and that's with a full conduit. I can see more things underwater from above the water now.
[media]Above is a picture taken from one corner of an underwater monument/guardian farm, with full conduits on each side. Before the last update I could see the entire monument/temple/farm and now I can't even see halfway.

The fog being thick when you first enter the water and gradually thinning out was an intended change mentioned in the the 1.19.0 changelog (cp. MCPE-124282).
Added adjustable fog effect that can expand or shrink over time. Users will get the sense of eyes adjusting when going into water
Using a stopwatch, I found that I could see glass blocks 30 blocks away after 6 seconds, and I could see sea lanterns 50 blocks away after 24 seconds. So I think the visibility is the same, but the adjustment takes longer than it should. The disparity from Java on the adjustment time is reported at MCPE-153864.

Still an issue In 1.19.60 & 1.19.70.21 Preview

Affects 1.19.63

Affects in 1.19.83, 1.20.0 & 1.20.10.20 Preview

Affects in 1.20.10.21 Preview

Affects in 1.20.10.23 Preview

Affects in 1.20.20.20 Preview

I'm the reporter of MCPE-187706. I vote for this report.
(*App Ver. 1.21.51.01, Device used: Sony SOG09 Xperia5Ⅳ Android14/Translated)

Thank you for your report!
After consideration, the issue is being closed as Won't Fix.
Please note that this is not the same as Working as Intended, as this bug report correctly describes behavior in the game that might not be the intended or desirable behavior, but it will not be fixed right now. Sometimes, this is because the issue reported is minor and/or impossible to change without large architectural changes to the code base.
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This is only for underwater caves