The only reliable way I've found to get rid of slugs and snails is salt.
That's just cruel. I remember my young daughter read somewhere that salt kills slugs, and she wanted to try it ... after some debate, I let her, and her immediate response was, "I wish I had listened. I wish I hadn't seen that."
I think it's the violence of gardening that appeals to me. The lizards eat the squash bugs, the ladybugs eat the aphids, the chickens eat the ants and the tomato hornworms, and the black widows eat the roaches. I'm trying to find some wasps to get rid of the peach tree borers. Then of course the peas and pumpkins try to strangle each other. Among the vegetables, the survivors get eaten. By me. I am the apex garden predator.
For the slugs, I don't go hunting them. Instead, I pour a little ring of salt on the ground around what I want to protect, and the slugs go elsewhere. I don't recall having seen any little sluggy bodies around so I don't think they're kamikaze'ing in order to get at the marigolds unless their little buddies are hauling them off for a decent burial.