Lightning sounds like an excellent option against these creatures.

[Well. As long as they aren't wet and standing right next to them when the magic flies.]

I have green magic. I should be able to coax the underwater plants into wrapping around the creatures so we can pull them closer to shore.

[That still doesn't answer the question about bait...]

They are flesh-eaters, so we could use fish or an animal carcass. ...Or ourselves.

[He's not fond of that last option, but he has to put it out there.]