"潜水""灌水""发帖""隐身"怎么说

隐身:
For forum purposes we call them 'lurker' or 'lurking'...

Not sure what the regular meaning should be.

发帖:
Post.

灌水:
I'm assuming this is when you make a lot of posts at once, so: spam post.

潜水:
Not sure what this means in Chinese.