Round 1 & 2
Octar, badly hurt, feels obliged to content himself with his bow, despite his friend's peril. Pulling back the beautiful recurved bow, Octar releases his shaft. The arrow makes a splash at the edge of the column of water, but continues flying, shattering against stone in the darkness.
The spell casters begin their mystical incantations. A pale red waraxe appears next to the elemental and swings, but seems to merely splash through the shimmering, shifting column.
Round 2
Marcus pauses momentarily at the base of the stairs, to see what the elemental will do. He doesn't have long to wait. Surging onto the stone flaggons, the column of water leaves the river, although a trail of water marks its path. Marcus draws his weapons and readies himself to avoid any attack. He anticipates a tendril of water slashing out towards him, and his instinct is correct. As the water bursts towards him, he drops underneath it and he feels only the cool mist of a light spray splash over his face.
[I interpreted Marcus's action as a full defensive dodge]
The rest of the party continues their attack. Octar's arrow again passes through the vague watery outline. Brioc's fireball fizzes out against the stone floor. Ehldannis' shark appears in the dark water, the darker silohette of its dorsal fin shooting about, vainly seeking its prey. Dhormium's axe follows the elemental onto the shore, but swishes though air on its attack. Only Tullius's arrow seems to strike through, lodging momentarily in the column of water, before dropping down and washing into the river.
Dhormium still has a second round action. Ehldannis may want to rethink his.