Project Malcom
I've read the topic about the glitches that can occur with the airboat. I know you aren't supposed to use any vehicle in Portal at all. But I just found the idea to be so exiciting, I've started to experiment with it.
http://bce100156.bcecht.org/portal/screenshots/ricotezportalairboat01.jpg
Of course this needs very carefull map design, to prevent any bugs from occuring. To start, the cleanser you see will only erase portals (and it even does when you pass it while in the Airboat). The box incinerating cleansers (if any) will all be on places you can't reach with the Airboat. As far as I have found out, it is not possible to get the Airboat through a portal, simply because it's too big, but that needs more testing.
I might consider adding some kind of forcefield the airboat can't pass, but I will try that out later.
Of course the Airboat has a skin that doesn't really match the remainder of the Enrichment Center, and since I can't really skin, it will probably stay that way. I will see what I can do, tough.
Then remains the question: why would you want to do this? That's an easy question with a simple answer: Because I Can.
Remember this is an experiment, if I can't get it properly working, I will skip the whole thing.
"Duct Tape is the answer."
The usual answer :
If it's fun and easily understable to the player, anything's possible.
Except passing the ship through a portal, it's too big :p
To be fun, your map should probably be like "route canal" in HL2 : you have to do some hovercraft for a while and then are blocked, and have to solve puzzles to allow the hovercraft to continue, and the exit could be reached only while aboard the hovercraft.
I think it could be fun.
As you said, the killer optimization would be to reskin the hovercraft in white with aperture science logos. But I don't knwo how to do that.
NO! THE CAKE! NOOOOOOOO !
For gameplay: well, one of the special techniques you'll have to use is changing water levels (in certain areas, not all). To do that you must press certain switches. I've created a custom skin for those switches (blue button), but I can't find a way to implement them in my map as a "skin1", next to the original red skin, since I still want to use them, either. Next to that, I've bought a professional mic a little while ago, I'm now experimenting with programs and trying to let myself sound like GLaDOS.
For the airboat skin: I'll try something for that one really soon. It shouldn't be as hard to implement as the custom switch since it will replace the original skin.
EDIT: first tests with custom skins are succesfull:
http://bce100156.bcecht.org/portal/screenshots/ricotezportalairboat02.jpg
It isn't visible very clearly, and done poorly, but I've slightly changed the colours and looks of the floaters of the airboat. For a start they no longer have rusty specks, and they're gray instead of the white-brown-greenish of the original skin.
"Duct Tape is the answer."
Well, I'm really making some progress on changing the airboat skin:
Though it still needs major editing, it is really showing some progress. My main target is to remove all the rust and give the boat a different colour (mainly white), later on I'll add Aperture logos and such.
"Duct Tape is the answer."
Maybe Flash Corridors?
...but since I'm already posting: If the elevators in your airboat map are for changing levels you could have the player get out of the boat, go on the elevator and get in a new one in the next level(or somehow let the player watch the boat being transported to the next level).
If the elevator is in the middle of a level then you could have it open one way when you get on and then the back of it would open where you need to get off.
And here we are.
Hmm, now that's a good idea! Having some kind of special transport for the Airboat! Will see what I can do...
"Duct Tape is the answer."
Gosh, triple post...
But, whatever
I'm gonna give my airboat map something you don't see on all custom maps: a backstory! Here are a few things I might put in:
-The testchambers are part of the Aperture Science Aquatic Testing Range, a secondary facility functioning completely on its own but still connected to the Enrichment Center.
-In this Aquatic Testing Range, you are assisted by the Male Acting Living Computer, also known as MALCom. You could see it as a male version of GLaDOS, but he's certainly not. GLaDOS is his superior, and MALCom has to listen to her. Even though MALCom is in control of the Aquatic Testing Range, GLaDOS can, at any time, take away control of him.
-MALCom has a different personality than GLaDOS, and will have a different kind of humour (mine).
-Don't expect GLaDOS to play no role at all! (At least, if I can mimic her voice)
-The Aquatic Testing Range looks slightly different from the Enrichment Center. Far bigger portions are made of metal, with the Portal Gun being less important than usually, since there is also focus on the Aperture Science Water Traversing Airboat. But don't expect the Portal Gun to be useless! The portal puzzles will still dominate the test chambers!
-In the Aquatic Testing Range you will find different technologies, which are all tested by MALCom. You could see the Testing Range as a place where beta apparatus is tested, before it is transported to the Enrichment Center.
-The Aperture Science Aquatic Testing Range is located near City 36...
"Duct Tape is the answer."
This is starting to sound pretty sweet. 
Okay, have been experimenting with Hammer and Dance eJay over the past few weeks, and got some things.
To start, I've finally created an effect for the MaLCom-voices I like.
http://www.fileden.com/files/2007/5/5/1049791/logicsense.wav
Unfortunately, Dance eJay made the file terribly big (1.1MB). Note that this was not an attempt to mimic GLaDOS; I deliberately tried to let MaLCom sound different. Also, the voice is not a generated one, I recorded my own voice and used that one instead.
What would you guys advice me to do to make the file smaller? Also, how do I add subtitles?
"Duct Tape is the answer."
To start, I've finally created an effect for the MaLCom-voices I like.
http://www.fileden.com/files/2007/5/5/1049791/logicsense.wav
Unfortunately, Dance eJay made the file terribly big (1.1MB). Note that this was not an attempt to mimic GLaDOS; I deliberately tried to let MaLCom sound different. Also, the voice is not a generated one, I recorded my own voice and used that one instead.
What would you guys advice me to do to make the file smaller? Also, how do I add subtitles?
first of all. sounds REALLY good; good job. secondly. to fix the file size. i don't know what options your audio software has. but all voice sounds in the game are in mono and thats all they have to be. because they orriginate from ONE spot. and the game simulates its location (stereo) in game. also. almost HALF of the sound file is silence (about 2.5 seconds out of 6 total) and... in a wave file (.wav) silence, and sound take up the same amount of space. so. i remade them for you. and if you record in 8bit mono (instead of converting AFTER you record) most sounds will sound close enough. BUT: Game voice sounds are 16bit, mono, 44.1khz sample
the first one i deleted the silence and merged the stereo sounds and converted the sample rate to 16khz and an 8 bit sound (its AMAZINGLY smaller and sounds "ok")
59.9 KB
http://www.fileden.com/files/2008/2/24/1778662/logicsense2.wav
the second one all i did was delete the silence and merge the stereo into mono and its sounds exactly the same, but MUCH SMALLER
327 KB
http://www.fileden.com/files/2008/2/24/1778662/logicsense3.wav
Wow... I figured out how I can trim samples and make them mono, and the files are far smaller now! Though I didn't get them as small as you, rellikpd, they are all at least half their original size.
"Duct Tape is the answer."