Wall of Water

[Miriad]

What actions are possible inside a wall of water? Can I cast a spell? Activate a magic item? Or is doing the swim check the only possible action?

[Threadnaught]

It depends on the thickness of the wall. If the wall is at least 5 feet thick, then you should be able to swim in it and not just through it.

Any thinner however and you'll just be moving through it. Though it is at least rough water. Depending on the caster who created it, the concentration DC would increase drastically for any spells a character attempted to cast.

Edit: I'd rule that you had to roll for each round you spent inside the wall. Everything you can do while swimming is okay.

Though every DM is different, ask yours... Unless you're the DM, then decide yourself.

[Beheld]

What actions are possible inside a wall of water? Can I cast a spell? Activate a magic item? Or is doing the swim check the only possible action?

If you are using the SpC Wall of Water, then you can take any actions you could have taken under water.