This guide will let you know where to find Bulb Bush Samples in Subnautica.
Starting from the coral tube sticking up out of the water, you have to make your way about 2 bumps to the right of the northeast until you reach the bulb zone.
It is recommended to have an Mk1 depth module, a high capacity O2 tank, a sea glide, and you will also need a knife.
The two main threats you will encounter in the bulb zone is the ampeel; you have to avoid it. And the bone shark, which you can either avoid, use perimeter defense against, or kill using the knife and stasis rifle.
The coordinates for this location are (1117, -268, 568).