
Decoy tube upgrade is pretty useful to that end.
Remember that avoidance is always the better option if you can manage it. Think of it like a perimeter defense - flick it on just before the leviathan makes contact and it'll zap him a little. It can completely drain a fully powered cyclops in under 2 minutes. Install the shield, but never turn it on until you absolutely have to, and don't leave it on. NEVER forget to turn off silent running when you park. Go slow if you are (it's both quieter AND more energy-efficient). Don't use silent running unless you're trying to slip past a leviathan. There's a free one lying around somewhere (Aurora iirc), but it's not terribly hard to build either. Don't bother operating it without the engine efficiency module. It's going to be slow, but it's useful for bringing the world on your back, including growing food inside it (wall planters with marblemelons, pots with bulbo trees, etc). See it as a mobile base/cargo ship, not a transit vehicle. Nor have I advanced the main quest super far (Sunbeam hasn't come by yet). I've found a few entrances, but haven't explored deeper into it because ghost leviathans + squidwert's shockwave are scurry. Note that the farthest down I've been is the Lost River.
I'm just trying to find reason to ever use it when I feel like the Seamoth does it all, faster, quieter, and with a cool shockwave that scares off leviathans. The shield drains all of the cells in like 12 1/2 seconds. Except I have to swap out all of the powercells after 10 minutes of play even with the efficiency module. Why is it a thing? I keep thinking, oh, I'll install some stuff and make it a mobile base.
Goes slower, uses an absolute metric butt-tonne of power, and has like no offensive capability. I built a Cyclops and have a few upgrades, but still feel like it's completely worthless. I'm about 45 hours in, but taking my time and exploring.