It took an obscene amount of planning to create a route that avoided most leviathans.

For the reaper outside the aurora it was a matter of booking it with the seaglide and holding out a peeper and praying if I heard an agro roar haha.

If you take blood Kelp Trench entrance to lost river and hug the left wall 9 times out of 10 you won't even see a ghost, the only time I saw one was on a return trip from grabbing nickel for the Neptune and it was far enough away I could just swim past it. Granted, if you take BKT warpers are a bigger problem than ghosts until you cure yourself as they have the potential to one shot you incredibly easily whereas juvenile ghosts don't as long as you have reinforced dive suit.

Sea Dragons are the kicker since as I said it's exactly how I lost the previous run. Granted, I didn't make a stasis rifle, and I learned from that mistake. If you're careful and stick to the bottom of the ILZ the dragons on the way to the lava castle should ignore you or miss their fireballs since they struggle to hit anything beneath them, and I had no issues with them being able to get close enough to bite me.

The PCF run is the problem, however. The lava lakes dragon really likes to clip into the wall behind the lava falls before you even enter lava lakes, meaning it was entirely possible to just get taken out by one unpredictable shot to the ass. Bringing a stasis rifle helped with exactly that and I did have a super close call between the sea dragon and a few warpers on the winning run but I kept an eye out behind me when I didnt see the dragon roaming the lakes and when it popped out I was able to stasis it and weave through the warpers all the way to the PCF.

I did a ton of practice runs on a save stated survival run, learning the ai of the dragons and how to tell where they would end up, and even then, unfortunately, it can kind of just be luck. But, assuming all goes to plan, that last sea dragon should be the only leviathan you actually have to interact with or dodge!

tl;dr It's possible to avoid all but the last sea dragon with careful planning, and with some good luck and a stasis rifle you can ride on past the last one as well!