OP has referred to pipe cavity "A" and pipe cavity "B." I don't read that this as a "pipe" that a submarine can navigate into as posed by some after OP said the Israeli sub entered, or attempted to enter the pipe cavity.

Opinion: The well pipe(s) from Well "A" and Well "B" have developed cavities where the pipe entered the seabed. The cavity(s) is the crack in the seabed which has grown large enough for a submarine to scout and report back with information. OP reported one pipe has collapsed, which I take to mean has completely disappeared into the cavity.

"Rim" is the edge around the cavity where submarines cannot get too close or there is unusual gravitational pull which negatively affects operations. The Israeli super-sub is the only one which could dive deep enough and counter the gravitational pull to enter the pipe cavity, where it was blocked. Due to this, that sub may not be, at least partially, non-operational.

"Splash Zone" are those immediate areas directly affected by the micro-organism emerging from the cavity. Initially, the organism drifted upwardly in column formation, but has recently jumped over into the spreading underwater oil plume.