Where the Leeches Are in How to Fish - Island 2 Leech Locations

Leeches are the quest item of Island 2 in How to Fish: five of them spawn on the ground and you hand the full set to the farmer NPC to move the main quest forward. Almost everyone who gets stuck here has the same problem - they searched the whole island and found only four.
Where the leech task sits in the main quest
The island order in How to Fish runs: starting island, Island 2 (the 5 leeches), spider crab, piranha island, pufferfish, albatross, final island (the bowhead whale). Collecting leeches is the core task of Island 2 and the first real roadblock most players hit.
Before you start collecting, make sure you already have the shotgun - the quest line moves in that order: get the shotgun, find the leeches, hand them to the farmer, fight the spider crab.
How to find all 5 leeches quickly
Every leech spawns on the ground; when you see a small strip-like object on the floor, walk over and interact to pick it up. Sweep the island on a fixed route: walk the island edge first, zig-zag across the middle, then check behind buildings and rocks.
The most common trap is a miscount: you think you have five but only picked up four. Open your bag and confirm the number before handing them in, and save yourself a trip.
What to do after handing in the leeches
Once the leeches go to the farmer NPC, the next main-quest step is beating the spider crab boss. Remember that the turn-in is the boss trophy, not ordinary meat - keep the spider crab drop in your bag until the quest asks for it.
Every creature also has rare variants to collect, so keep an eye out while you are on Island 2 - miss one and you will have to farm the island again.
FAQ
Where are the leeches in How to Fish?
Island 2. All five spawn on the ground on the island - walk up and pick them up, no fishing needed.
I cannot find all the leeches - what now?
Fewer than five means spawn points are still unvisited. Sweep the island edge and every corner again - the spawn spots are not in a fixed order, so the one you missed can differ each time.
Who do I give the leeches to?
The farmer NPC on Island 2. Hand in all five to advance the main quest and open the next steps and the next boss fight (the spider crab).
What comes before the leech quest?
Get the shotgun first. Once you have it, follow the quest line: find the 5 leeches on Island 2, hand them to the farmer, beat the spider crab, then turn in the trophy.