One of the things that fascinates be about sound under water is that, contrary to what one of the narrators seems to be saying, to humans anyway, it's omni-directional.

without listening to the program again, I sort of remember that part - I think they were referring to a special case of the source being next to a large flat surface, such as the sea floor or a cliff face. Of course you'd then a hemispherical radiation field instead of the usual full spherical. But apart from that, you're obviously right: sound is radiated omnidirectionally underwater, given reasonably isotropic conditions.

More to the point - you've experienced something which I've only heard on programs .. wonderful. Maybe I'll get into scuba diving one day .. but being my paranoid super-careful self, I'll definitely take some type of anti-shark weapon, like a stun gun!