I can't get into the Lost River...

I have a base in the Northern Blood Kelp Zone and I'm trying to get in through the trench, but I keep having to fight off waves of blood crawlers so that they don't destroy my PRAWNs and seamoths, which I can't dock because I don't have enough resources to build a moonpool. Today a ghost leviathan came too and destroyed one of my PRAWNs, which made me realize my need for help.

The problem is mostly the fact that if I leave to get the resources to build moonpools (the reason I'm going), the blood crawlers and the ghost leviathan will smash all my vehicles to pieces.

But if I don't go, I can't build moonpools to protect them.

And I can't even search the remaining parts of the Blood Kelp Zone, because then who will protect my vehicles? I tried a gravity wall, but it failed. It caught a few blood crawlers, but then the remaining ones were able to push through, and my grav traps hooked onto a ghost leviathan and it pulled them away.

Can anyone offer an idea of how to protect my vehicles from the horde?

Another question; WHY ARE THERE SO MANY BLOOD CRAWLERS?