There was definately an invisible rock inside my bridge, with those fishes flocking around and away from me as I played Tarzan inside my blocked bridge. I could even see the rock carving animation outside of the hull, through the bridge glass. I jumped frantically, wielding the knife around. IN a final move I tried going at it inside my bridge, with the knife. I was on the point of deleting my save file and starting all over again. The propulsion cannon trick did NOT work. This bug had me into despair, tried everything posted above. You have an invisible obstacle in the bridge, that you need to parcours around, but also there is this horrible collision sound when you run around it or even when you just pilot the Cyclops around. There was an invisible rock inside the bridge of my Cyclops, (ghost) fish circling all around.

How can I get rid of it? It is driving me nuts with the sound! And the constant fish around it aren't helping either. Inside it when I am outside, outside it when I am inside. You can also hit the block with a knife while inside, but the cyclops tends to freak out and jump out of the water sometimes when you do. I can also use the propulsion cannon to pick it up whilst outside the cyclops, but not inside, and cannot seem to shoot it out of the cyclops using the propulsion cannon as far as I can tell. It is currently inside my cyclops bridge, and I can use the stasis rifle on it while in the cyclops or out (if you do the cyclops can no longer move more than a few feet until the effect wears off as the block hits the walls of the bridge). The second was caused by the medkit fiasco, but I have discovered through experimentation that the original problem above, the invisible object in the bridge and the crashing sounds, is in fact caused by the invisible block that the particle effect fish spawn around. This discussion's a bit old now, but still relevant to me at least.

Subnautica cyclops stuck in shallows