The door doesn't last long after a few good kicks from the party. Lightfeather gives the bolts a few chops, and Garadh gives a strong heave with his boot, moving the door off its hinges and snapping the spear trap at the same time.
A few more tugs frees the door entirely just as the water begins to lap at their boots. Past the door, the party sees a long stairwell going up into the darkness above, which should be enough for them to avoid the rising water.
The skeleton nearby is nearly carried off by the rising water, causing the armor it is wearing to smack against a side wall and flake off some of the rust from the suit. There is a gleam of bright metal underneath, and Thuk believes that it looks as if the suit was well built enough to avoid the effects from ages of corrossive water. If so, it must be quite well-made and potentially valuable.