Creating underwater scenes is one of those things. You need to know how to do it. And it's also quite easy to do, especially with 3D Studio MAX. MAX has a lot of features built in that are very useful for creating those ship-wreck environment. This tutorial shows you how to easily build a believable underwater-environment, and you need to know how to use environment effects (fog and volume lights) and a few features in the material editor. Finally, there will be a few extra tips for you Sand Blaster users out there. I will also asume you know the basics of 3D Studio MAX, so I won't go into how to scale mapping coordinates and such things. I will also create a ZIP-file which you can download at the bottom of this page, which will include materials, maps and scenes. Ok.....dive in!

Step 1. First of all, we need the ocean-floor. Create a box with these measures:

Length: 200.0

Width: 200.0

Height: -5.0

Length Segs: 75

Width Segs: 75

Height Segs: 1

With this, you have the basic element of your floor. To make it look more natural, or "not computer-generated", add a noise modifier to it:
 

Ok, now we need the material. This is actually quite easy, because the material I use for this tutorial is the standard Sand Texture you find in the default MAX material library. So there is no need to include that map in the ZIP-file. Apply the material to the ocean-floor and apply an UVW Map modifier to set the mapping coordinates. Scale the mapping any way you like it. Now, we're ready for a test-render:
 

Ok, so now we have the ocean-floor. This is just one of many steps, so read on.

Step 2. Next we need to think of how things look under water. One thing we have to think about, is that we can't see very far. This is due to light having to travel through water, which is substantially more dense than air. Thus, we have to create the notion of water in our scene. This can easily be done with Fog. Go into the Environment dialogue box (on the Rendering menu), and add a Fog effect. This should have these values:
 

Note that the fog-colour is (R: 58 G: 91 B: 99). This colour will make it look dark, yet not too dark. If your scene is way down (like thousands of feet) you could use a darker colour. You will have to experiment with this to see what fits your scene. Here is another test-rendering:
 

Step 3. Next, we will add the underwater light. Remember those Flipper-episodes? With the light under water? This is called Caustic light. This appears when light is refracted through the water with it's ripples and waves. This can also be done vert easily, with a projector. I will also include the image I use for the projector in the ZIP-file at the end of this tutorial. (The name of the map is caustic.jpg).

First of all, create the light-source. This should be a spot-light (or directional light, but I use spot) some distance away from the ocean floor:
 

Go into the material editor, pick a free slot (I picked the 6th slot), and add a new material; choose Bitmap. The way to do this, is click the "Get Material" button, and pick a "Bitmap". Now, in the empty Bitmap-slot, pick caustic.jpg (remember to put the map from the zip-file in the 3dsmax\maps directory). That's it for the material. Now go to the spot-light again, and turn on Projector. Next to that, click Assign and choose the caustic.jpg map from the material editor (I said earlier I won't go into these things, because this is basic MAX stuff). Here is the material settings and the light settings:
 

We're ready for another test-render:
 

Next, to make it look like the water has some substance, add a volume light to the spot-light. This is done in the Environment dialogue box (in the Rendering menu). Add a new effect, choose Volume Light, and pick the spot-light for it. Also, set the Density to 1.0, or the scene will look completely white. I also use completely white for the fog-colour, but of course you can experiment with this to see what fits your scene. The light will now cast faint rays that make the light look like its really traveling through water.

And that's it! This is the basic stuff for making underwater scenes. Add rock, ship-wrecks, whatever to make this look like an underwater scene. Of course, no sea life is pretty dull, so read the Sea-Weed and Sand Blaster sections further down to se how you can add more life. Anyway, here is the final render for this scene:
 

The mesh for this is included as scene.max in the ZIP-file. Remember to put the caustic.jpg in your maps-directory, or it loses some of it's impact.

Here is a small tip for you: if you have a mesh of a weed or reed of some kind, it's quite easy to make it look like sea-weed. Here is a Reed I created with Silicon Garden (for 3D Studio R4) and also scaled in the z-direction:
 

Next, to get that "underwater" look, just put a Wave spacewarp on it. Here is the waved reed:
 

The mesh for this reed (with the wave) is included as weed.max in the ZIP-file.

Ok, now it's time to roll out your Sand Blaster. If you don't have SB, this section is meaningless. However, this is also achievable woth normanl MAX features; it just takes a lot more work. This section will show you how to make bubbles with Sand Blaster.

Ok, imagine you're making a scene with a diver or something else that might need bubbles. With Sand Blaster, this is quite easy. Let's say you have a broken air-hose. This will most definately create bubbles. For this, I start a new scene, and make a tube just as an example):
 

Also, as you know if you've been using SB, you need an emitter. For this example, I place a small GeoSphere at the mouth of the tube. I also place the SB system, and rotate it in place:
 

Now please remember to hide the sphere, as it only serves as an emitter. If you hide it (under the Display-tab) it will still affect the SB-system.

Ok, to set up the SB-system, you will have to tweak this at your own. For this tutorial, I set both Particle Activation and Render Activation on, and leave the particle number at the default count of 100 (I will not show a screen-shot of this, because the rollout is pretty intimidating in size). Under Render I set the particles to be Spheres, and change Particle Scale to 5.0 and Scale Variation to 0.3. This means that the spheres, or bubbles, will be somewhat varied in size. These numbers might need other counts in your scene, but this is what I used. And that's it for the particles. You also need a material for it. That will also have to be adjusted to your scene, so I won't go into making that. However, it should be transparent, and maybe have a faint reflection map (just a bitmap will do). Here is the rendering of these bubbles at frame 30:
 

And that's it. The mesh for this is included as bubbles.max in the ZIP-file. If you load this without SB installed, you will experience errors.

Additional tip: This technique can also be used to create swarms of fish. Just make one fish, and use that as a custom particle. If you do this, please mind the orientation of the particles. Set it to follow the path. You also want to create a target as well, so that the particles (fish) flow from one point to another.

Throughout this tutorial I have used several techniques, and also a map you might not have. Therefore, I have compiled a ZIP-file with all three scenes (scene.max, weed.max and bubbles.max) and the caustic.jpg map for the caustic light. Download examples.zip here and take a look first-hand. Please not that you will need the caustic.jpg map in your maps directory to render the main scene. You will also need Sand Blaster installed if you want to look at bubbles.max.

Here is an image I created a while ago. It is an underwater scene where I use all of the above techniques.