Which undersea summons are worthwhile?

[Meglobob]

I only really use sea trolls and battle summoned water elementals (living water) when fighting underwater. I always try using shark attack and friendly currents with them.

If you can get the 3 water queens then they should be your priority for your water gems.

Items like boots of quickness, jade armour, bottles of living water, water braclet and robe of the sea are good items to forge with water gems.

Finally, the global Maelstrom is perhaps the best gem producing global in the game, as it produces the most gems, 27 gems per turn in total. The drawback is 15 of them are water gems and its Evo 8.