"I just think that anything outside of the imapct zone would be able to literally roll with the punch and survive, as opposed to being on dry land, but tell me otherwise."

You might ask yourself where would you go if you knew a 100 km impactor was going to hit Earth.
There is no easy answer, I don't think.
But probably being in the air- an airplane which could fly high and could stay up for awhile. Caves maybe would be better, but it would have be able to withstand very severe earthquakes.
Simply having very good luck and perhaps a parachute might work.

In the ocean you wouldn't have much problem to do with the flash, but the water is going to carry the concussive shock- and no doubt you would hear it.
If I'm recalling correctly, 1 km diameter rock hitting the ocean will create a supersonic and sonic wave of water which creates a wave of about 1 km high as it nears land and this wave of water will travel "as fast as jetliner".

A 1 km rock not really comparable to the nuclear underwater tests- because you dealing with a lot more energy- hundreds of thousands times more energy.

I would say that the kill radius in the ocean would be more exact- you could be safe at a certain distance and 100% dead nearer. On Land you also have 100% kill radius but going beyond that you have 90% kill radius, 50%, etc.
But if you have a impactor big enough for 100% or 99.9 kill radius anywhere on land, I don't know if you going have a much better chance if you are in the ocean from that same impactor.

But as far as humans go, with the bigger impactors, it's more human dead if it hits the ocean rather than the land- mostly due to our cities on the coasts.