Already tried a grappling encounter, and it was good because it gave the Cleric a chance to do their stuff. The cleric's a dwarven follower of Desna with the Liberation and Travel domains. His 8th level domain power lets him automatically suppress the confused, grappled, frightened, panicked, paralyzed, pinned, or shaken conditions as a standard action.
Traps are fairly common, and I use a mix of both simple Disable Device check traps as well as puzzle traps that require thinking instead of dice to solve. I usually include them in an encounter with enemies, for example a hallway with an automatically resetting lightning based trap with a pair of bodaks inside who are immune to that energy type.
I think I might be overthinking things too much, but I guess I spend a fair amount of time prepping encounters, learning the monster's special abilities and crafting a list of loot for it, only for the samurai to come in and full attack it, taking it out in two to three rounds. Combat seems to be getting a bit formulaic in that respect. About the only thing I do have going for me is that nobody in the party has any AoE damage, so swarms of mooks with one or two big baddies is still a viable strategy.
Edit: Regarding water levels, the party treat anything involving travel through liquid like it's a death sentence. The current dungeon I created had both a sunken ship near a ruined dock at the very start, plus a secret entrance leading inside the necropolis that was through an underwater passage. They ignored both options and simply charged through the massed defenders at the front gate.