I work in exploration of the continental slopes (there's a damned good reason for my vessel to have holds capable of carrying 3km of riser pressure-rated to 20kpsi). It's on-going. Unfortunately the costs are much higher than for exploring, developing and producing in shallow water, which is why only the highest-quality prospects are worth developing.
Unless you believe Tom Gold (which would get you laughed out of any board room with a geologist in it), you need sediment in considerable quantities to generate significant quantities of hydrocarbons (note below). After which, looking at your hypsographic curve you'll see that the 5km water depth contour (OK, "isobath") encompasses something slightly less than 5% of the Earth's surface while the average depth of the oceans is 3800m.
And now you know why the commercial vessel I work on (one of 4 sister ships, built to the same basic design) has space for 3km of marine riser, and the largest vessels on the slipways of China only carry 5km of riser.
Some early explorations were discouraging, but MOST exploration is discouraging.
In intensely planned remote area deep water offshore exploration, the discovery rate is about one well in three.
I was discussing a previous well with another vessel's weather forecaster (that'll tell you which region we were in) who informed me that core was brought to the surface on three occasions which was oozing with oil; my geological sources refused to comment (quite correctly) several years later when I quizzed them about it, which I take as confirmation. A discovery! Yes. The prospect and regional license was abandoned. The discovery wasn't big enough to have a chance of repaying the billion dollars poured into finding it.
Welcome to offshore exploration.