In Giants, Double Trouble's Soul Gem is pathetically and literally useless.
"Waterwalker- Double Trouble can fly over water." Um, there is no water AT ALL in Giants, so...
Best? Maybe Hex or Camo.
Hex- The Skull Shield really helps fend off meleers, and it ticks very rapidly for either 15 or 35 damage, I forget atm.
Camo- Yes, the shield really does help also, in a similar way to Hex, except Camo heals 5 health every second.
BOLD: You know there's some Heroic Challenges with water, right? (I.e. 's HC, and some others I can't really think of)