Echo

[Todd]

Hi, let me give you some comments on your revision.

First off if the title is echo than it doesn't work well also being the last word of your poem. The title sets up the echo so the last line needs to more of the sense of the idea without being the word. Just an opinion, not sure if that makes sense.

Echo

Lay bare on moonlit water,--The first two lines read as commands with an implied "you" as the subject. So this first line should probably end with a period. This first line is pretty phrasing.
Gently sway with salty breeze.--It's not that you can never use adverbs or adjectives. It's just when they are unnecessary or better expressed as rephrased nouns or verbs than they should be cut most of the time. Sway implies a slow rhythmic movement. Why would you need gentle? While salty breeze does add a quality not found in all breezes, there's probably a better way to get there. There are literally thousands of approaches. You're looking for more interesting phrasing. The problem with most modifiers is they read like easy shorthand not really as effective imagery.
If in every shell resides a ghost,--So this is your key proposition.
Is there nothing more than a echo?--This isn't asking for a question. It's asking to be led with "than" and making a statement or observation. Really think about what you're trying to say and reword.

I know I wrote a lot, but most of what I wrote is just trying to give you enough clarity on what I'm talking about. I hope the comments help.

Best,

Todd