Re: Stealth
As Roxis said, you can only hit them if you stand directly above, left, right or below (as seen on the screen), or, alternatively, only in squares that are connected by corners, not ones connected by edges. I am actually surprised that your gal in the diagonal can see the target.
Re: Lobstermen
Usually, if you need more power to deal with something, you need to use melee weapons. Especially hammers. Hammers are really good damage-wise, especially if you have strong gals. Otherwise, Piratez is not XCom, you are not trying to stop all the "UFOs" from flying over the earth, you're trying to intercept some and make a profit. If it's not going to make you a profit, don't intercept it
Your score can likely survive it.
Also, Dioxine hinted that aquatic life-forms have a hard time breathing air. Imagine if it's highly polluted.. smokey? air.