I'd imagine that it is made more likely by the topology of the ocean floor itself; there are probably good corridors through which to travel undetected (especially in 'friendly' water where it's unlikely that the enemy have detector arrays). If both sides are using the same ocean floor map, it seems that the odds of a collision go up considerably if there's an obvious corridor to traverse/hide in.

Wolf3D used raycasting, rather than tracing to give a pseudo-3D rendering of what was basically a 2D grid map.

It's pretty clever how it worked, I remember having a LOT of fun cooking up my own similar renderer back in the day (Turbo Pascal with inline asm was fun!). If I remember rightly:
First, the ceiling and floor were drawn in, covering everything (intersecting in the middle, vertically). Then, they took your location on the map, and cast a ray for each row of pixels (320 of them, I believe). This ray went forward until it intersected a wall - and the distance to the wall was measured. It then did a quick calculation (lookup table) to determine the height of the wall at that distance, subtracted half that height from the center of the screen, and plotted a vertical line in the color of the wall. I seem to remember the wall color was retrieved from a small texture and scaled.
That gives surprisingly good results, albeit with no lighting or shading.