Hole In The Sea Effect

The first step would be to duplicate the footage and remove the water from the top copy, leaving only the boat and its wake (a simple mask and feather might be sufficient). The bottom copy would have the boat removed. You may be able to do that with a duplicate layer, a mask with feather on part of the ocean without the boat, then a position change and  Pre-compose the pair so you have a water-only layer.

Now, you need a displacement map for the ocean layer to distort the center and make it look like a whirlpool is starting. I would use a combination of Wave World, Twirl, and an animated mask as a track matte, blur, and probably levels to create a rotating displacement map that I could use to distort the waves and maybe even add some contrast. Combine that with an effect that looks like the ocean waves start spinning and the middle is getting darker. You may need to end up with several more layers and some masking. There is no one-click effect that is going to produce the kind of displacement map you need for the ocean layer.

The last step would be to animate the rotation and scale of the boat to make the 2D layer appear to spin, warp, and go down the hole and kind of look like a 3D boat. You may need more than one copy of the layer to add to the effect's realism.

The other option would be to download Blender, study and learn to use the app for a week or two, and do the whole shot with 3D models. Blender is more than capable of that kind of animation, and it's an open-source 3D app with tons of great tutorials. 

I think this is where stock footage can really help.

On Pexels, search for something like "waterfall from above drone".  

Download a few examples.  I did this really quickly, so the footage I got would need to be refined or at least tracked as the drones were moving.  But provided you can find decent footage, then bring it into After Effects.

Next create a new solid, and add:

• A Gradient Ramp.  Set the start and end points so that the edge appears in front of the boat
• Levels effect and adjust it so that the edge of the hole is quite sharp
• Turbulent noise effect to roughen the edges of the hole.

Set this layer above the boat footage with its transfer mode set to Multiply.

Add your stock footage layers, using masks and possibly the luma key effect to just show the white foam.  

Use the solid as their track mattes, set to Luma Matte Invert

Hey Luca,

It's kinda tricky because most of effects that are complex it involves 3D. However assuming that you don't want to change the perspective, you can try to use a distort effect that's called Bulge (play with the keyframes to make it from smaller to bigger), it will help creating that "hole" but keep in might you will have to mask out the boat since the hole will appear under it. Then you can play with mask and shadows again to give it depth.

That's my best shot, hope it helps.

Unless you intend to buy a ton of clips of actual waterfall footage to patch things together or get into complex 3D effects animation, I can see no realistic way of doing this. The footage isn't ideal to begin with, since it is by itself just a 3D rendering and not even a particularly good one. If you're settling for multiple levels lower you could recycle one of those "wormhole"/"vortex" tutorials on YouTube where it's all created with Fractal Noise and swirly distortion effects. Really depends on what you're aiming for, what the animation is going to be used for and how much time and resources you are willing to invest.

Mylenium