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In many games where the player can go underwater, it seems like when you look where the top half of the screen is in the air, and the bottom half the screen is in the water, it's almost like the water doesn't exist and the player is... flying slowly with water sounds?
Is there a logical way to solve this? An algorithm? Doesn't seem like any solution has come up yet since many games still have this. I don't want to make the same mistake.
How about simply not permitting this situation?
I don't know how you are making your game, but if you detect that the view will be partly underwater, you can force the camera to be above water, and only when the entire view would be below water, you can switch to the underwater view.
Depending on how you do it, this could mean that there is an additional delay from the moment where you start diving and when you actually view the scene from beneath the surface. This may actually be a good thing from a UX perspective, so feel free to experiment.
On a separate but related note, I wonder why most underwater scenes are rendered crystal clear... If you ever put your head underwater, you will notice that your eyes are not designed for underwater sight, and therefore everything seems blurry. You'd have to be wearing goggles to actually see clearly underwater.
And additionally, things look (and hear) very different underwater than above water. Water absorbs light much faster than air, so the farther light travels, the less light will arrive at your eyes. This means that the deeper you go, the bluer things look (red light has less energy, and is therefore absorbed more easily than blue light). In fact, at a mere 12 meters underwater, blood looks black, not red.
I've yet to see a non-specialized game that even tries to get underwater environments right...
The problem you are referring to has to do with the camera's view volume clipping through the water plane; typical "underwater effects" are done via full-screen post-process effects, and wouldn't look correct if the view is clipped like this (it would just be the opposite problem).
Even if you do bother to detect the clipping case (potentially difficult) and scissor or clip the otherwise full-screen underwater effect so it only applied to the underwater scene (which is a potential solution you could explore), you'd still have the problem of the actual water plane itself. The transition there would still be a jarring visual artifact. You could detect that plane and blur it heavily; this is probably the closest you can get to a real-world analogy of what the view may be through a partially-submerged camera lens.
Alternatively, prevent this from happening entirely: don't let the camera go below the water plane if the player is "above" the water or above the water plane when the player is "below" the water. This will only really work if you have discrete player operation modes for above/below water, and works best if there is a physical button or other clear and obvious action the player can take to transition between "swimming on the surface" and "swimming below the surface."
Instead of an explicit keystroke to dive, you could interpret forward motion while the camera is pitched down sufficiently to mean "dive." You can then use a graphical effect (splashes or whatever) to hide the camera's transition through the water plane, which it would normally not be able to cross.
We used a technique like this in Guild Wars 2.
Games usually turn on some sort of effects, primarily blue fog, when the camera is underwater. To handle the situation where the near plane clips through the water surface, you can turn on the fog shader when the camera gets close to the water surface, but then add some code to the pixel shader that calculates the point on the near plane corresponding to that pixel, and activates the fog only if that point is under the water surface.
If fog is done as a postprocess, by rendering a full-screen pass, this is especially easy - you just have to calculate the world-space position of each vertex of the full-screen quad or triangle on the near plane (with the inverse view/projection matrix), and interpolate this value down to the pixel shader; then you can check its vertical component and see if it's above or below the water plane.
For bonus points you can use the same technique to add a few-pixels-thick texture to represent the meniscus at the water surface, so it doesn't look so much like a sharp line.
I have two methods; One uses a shader, the other one could use a GUI. Both will start the same:
"Simplified" - If, Object(Camera) is in 3d Space(Water bounding box/whatever you choose) trigger a shader/GUI.
Shader will give more realism, you can apply a distortion Like This one
Fog Like Com. Boy stated, can be applied through GUI. Create a photo, with a partial transparency and use it as GUI on the entire camera view. For the photo you supplied I would try a brown colour.
This has been used in a horror game called Drea D Out. If the player approached a ghost, the screen would turn foggy. Although it wasn't used under water it gave a similar effect :)
You can always choose both methods, or make a shader that would change the colour.
Taken from : http://sahdan-share.blogspot.com/2013/04/dreadout.html
