I am going to start a map which is basically your average beach assault with a bunker, trenches at the top and of course MG NESTS. I am an average mapper. I am ok with basic displacements liek hills and stuff. I just cant get the right angels and also The silly landing boats the americans use are really hard to position so they dont look really fake and stuff like even on DOD_ANZIO made by valve if you lie down next to boat, it is hovering above ground. Also I don't know how to make it look as if the sea goes on for ever and I can't do 3D skybox's. I am a single player mapper for HL2 and have never mapped for multiplayer so I am good with scripted scenes and triggers instead of multiplayer action. But I will give it a shot.

Can anyone help me with my problems and give me some tips how to accomplish my goal?

ttfn,
Sadders
x

exaggerate the gradient and then use the smooth.

to make the boats not look like they are floating, just lower and adjust it until you are satisfied with the results ingame. trial and error
the water extending into the horizon is part of the 3d skybox, so you should read up some tutorials on that. better than anything i could say

for the boats --

click on your 3d preview window. hit ctrl-z to bring to fullscreen. position yourself at the side of the boat. hit 'x' and select the side of the boat. hold down 'alt' and use the mouse to drag the boat higher or lower ever so slightly in the 3d view untill its perfect