Graphics are nice. Like the voronoi pattern on the sea shader. Not exactly realistic, but at least it gives the sea some motion, and that's nice. The ships look detailed and interesting. The weak point of the graphics is PFX. Most of your PFX are PlayOnAwake(true) and PreWarm(true), which gives a jarring effect when they start. You can increase the simulation speed if you want them to spawn faster. It's in the main module.
The music loop is too short and therefore repetitive. SFX are fine.
I don't see where the theme is used. Could be that help will never arrive? I suppose. Bit of a stretch.
I had fun playing it and it has replayability. I didn't like the design of the shockwave pickup, as one of the main strategies for me is keeping the distance. So that pickup served no purpose. The AI also goes mental every now and then, spinning in place.
A decent entry.