Good game, great ending
If I had audio currently, I'm sure the music would be wonderful, too. I did deduct a point because of one annoying problem; when the close-up of the 'boss' whale takes place, typically the ball of fire will hit the player. I don't know if that's a flaw in the game of if I'm doing something wrong, but I got a 9/10 feel because of that, and other minor issues. Remember, 9/10 is still well above average! The game is excellent overall.
A lot of people will be offering strategy tips, so here's my take: there's no need to change weapons until the whale. I used the grenade launcher (weapon 3) for the boss in most of my playthroughs.
Anyone who couldn't figure out the "Do It Properly" achievement: Well, clearly the only way to be completely ethical in a game like this is not to participate, and that's exactly what the achievement calls for. Just don't kill anything that's not vomiting fire and you're good. It's more boring, but undeniably more achievement-earning.