Before We Leave

On one of your planets, for me it was the first in the tutorial, you will come across a one tile crystal island. In the beginning of the game, you can't really do much with it so leave it alone for now. However, build a Scout Ship and park it near the island for later use.

Once you advance through the tech tree and are able to build Submarines, be sure to upgrade your Shipwright. At level 2, you can build Submarines. These are used to explore derelict ships to find goodies. But, you can also explore the crystal island. Now is the time to save your game! Explore the island and take note of the bigger crystal island that spawns. Now, reload your save and navigate your scout ship to where the island will spawn. Once that happens, you will unlock the achievement.

Should you no longer be able to build Scout Ships, just build a new Shipwright and you should be able to as it will be a level 1 building.

Hope this helps