Hello ireland08,
You cannot get higher waves in SS08, at the moment.
There is a 'loophole' that some people have used, in V1.0, which is closed down in all newer versions.
With an illegal file edit, that will lose you your rights to technical support and your warranty, you can make the waves higher, but the ships will not behave realistic, nor will it look very good.
But if you really want to do this and want to run with just V1.0, then you can look here (http://www.shipsim.com/ShipSimForum/index.php/topic,982.0.html)
To know how to download, or upload, new custom missions, look here (http://www.shipsim.com/ShipSimForum/index.php/topic,4506.0.html)
But you need to have at least V1.3 of the game.
I hope this helps.
Regards,
Fred