Main tube de-focusses the lasers


I’m in that excited phase now, finished the build and can’t wait to drop it in the water. However, I spent ages focussing the lasers, only to find that when I put the whole thing in the main tube, the lasers were far from a point, more like a fuzzy line. Will this change when it’s underwater? I hope so, because there’s no way of focussing them when they’re in the tube.