If Namor occupies water terrain and is the only opposing character in range, can Pulse Wave be used against him?
Same as above, but he is not the only opposing character in range?

Namor would not be safe from pulse wave for the same reason stealth does not protect a single figure from being targeted with it.

PULSE WAVE Give this character a ranged combat action even if it is adjacent to an opposing character; the area of effect for this attack is half the character’s range. Draw lines of fire to all other characters within the area of effect, including at least one opposing character; these lines of fire ignore all game effects except for walls, blocking and elevated terrain. Game effects possessed or used by characters with a line of fire drawn to them are ignored until the action has been resolved. If a line of fire is drawn to more than 1 character, this character’s damage value becomes 1 and is locked. Each character hit is dealt damage.

Pulse Wave ignores game effect as it draws lines of fire ("...these lines of fire ignore all game effects"...). So yes, Pulse Wave can be used against him.

Yep, you don't have to "draw a line of fire" to activate pulse wave anymore. You simply activate the power now and it hits (depending on roll) every character within half of your range.

That's how I saw it, but since the first part of the sentence is "Draw lines of fire", it was ruled you can't draw a LoF so you never get to the ignore part.

That is the confusing part.

Pulse Wave don't care where you standing, what powers you got, how much money in yo pocket! It gonna hit ya!

That was my understanding as well.
Also, the character that was attempting to Pulse Wave ignored Hindering (and everything else). But I think if I tried a regular ranged attack, ignoring hindering wouldn't matter in that situation.

Namor's power doesn't work against PW

PULSE WAVE Give this character a ranged combat action even if it is adjacent to an opposing character; the area of effect for this attack is half the character’s range. Draw lines of fire to all other characters within the area of effect, including at least one opposing character; these lines of fire ignore all game effects except for walls, blocking and elevated terrain. Game effects possessed or used by characters with a line of fire drawn to them are ignored until the action has been resolved. If a line of fire is drawn to more than 1 character, this character’s damage value becomes 1 and is locked. Each character hit is dealt damage.

Namor's power is none of the things listed in the description of the area of effect. And it does not say it cannot be ignored, so it is

What? Did you read the power - PULSE WAVE Give this character a ranged combat action even if it is adjacent to an opposing character; the area of effect for this attack is half the character’s range. Draw lines of fire to all other characters within the area of effect, including at least one opposing character; these lines of fire ignore all game effects except for walls, blocking and elevated terrain. Game effects possessed or used by characters with a line of fire drawn to them are ignored until the action has been resolved. If a line of fire is drawn to more than 1 character, this character’s damage value becomes 1 and is locked. Each character hit is dealt damage.

You most certainly draw lines of fire. Period. End of story, Fat lady's aria is complete. If you did not and simply attacked the characters within the area of effect there would be no need for the part about what it doesn't ignore for line of fire