Desert Island

Bring the fish health bar to the white marker, then use a skill that is already attached to the rod you are holding. Clicking alone stops at that marker in the walkthroughs. If the skill is on cooldown, the finish waits.

The developer FAQ says to unattach the skill book from the old rod before attaching it to the new one. A quest can also want that book sitting in your bag, and turning that quest in can consume it. Read the confirmation: one unequip path returns the book, while a delete warning means the book is destroyed.

The developer FAQ says weather appears on the map every 30 minutes and despawns after 10 minutes. It does not give a clock time for the first spawn. Boss location also changes by island, so search areas you have already unlocked.

The experience description says joining the group grants an exclusive Fishing Rod Skin. Use the Fishing Master Community link on the official game page, group 67033518. Lotus Fan is a separate Mythical skin that also asks you to like and favorite the game.