Beat all da gym dudes and go to see route 3
How To Get Lugia In Pokemon Lake?
You'll find lugia in the sea route after you beat all the gym leaders.
Beat all the gyms and you will see him at sea route
You have to get all gym badgers inclidung the frointier brains and then go to the sea route 3 map and you'll find it there.
Go to toilet
There is no such thing as the Pokemon Lake. Sorry.