Trick to Explore Unexplorable Levels

When you try to explore high-level areas, it rejects you saying 'You can only explore up to Lighthouse +3.' (Image 1) In that case, warp to the middle of the map, click on a high-rank of the same type (this time, merchant ships), and it will show a message like 'Defeat Lv21 first.' (Image 2). Then, if you click 'Move,' you'll automatically warp to the Lv21 merchant ship. This feature is very convenient, so record the coordinates of high-level enemies. (Image 3) Tapping them will display the high-level coordinates. By using this, you can explore levels you haven't defeated before, as many times as you want. I defeated Monster Lv30 with 3 stars at Fortress Level 16, so Lighthouse Level 16 is definitely not enough. I wish they'd make this feature allow for more exploration. (´；ω；｀)