The Grandpa Horseshoe Crab is a Secret-rarity catch tied entirely to the Desolate Deep, the first underwater zone in Fisch. It is a luck-favored fish, so its odds climb the more Luck you stack, but it is one of the easier Secrets to land once you reach the right water. Despite the rarity tag, it barely fights on the reel bar.
Quick answer: Dive to Desolate Deep, then either harpoon it while it roams, set crab cages in the Brine Pool or Desolate Pocket, or fish the Desolate Pocket with a high-Luck rod. Spring with Clear or Rain weather gives the best spawn rate.
Reach Desolate Deep first
Desolate Deep sits below the ocean surface near Sunstone Island, and it is easy to swim past without noticing it. You cannot survive the depth without diving gear, or your character drowns within seconds.
Tip: Crab Cages cost only 45 C$ each and are sold at the Desolate Deep merchants, so grab a stack while you are down there for the passive method below.
Three ways to catch the Grandpa Horseshoe Crab
All three methods work in the same zone. Pick whichever matches your gear. The roaming method is the fastest if you own a spear or harpoon gun.
Roaming method (spear or harpoon)
The crab appears fairly often as a free-swimming creature in the water. When you see one drifting through the Desolate Deep, hit it directly with a spear or harpoon gun to secure the catch without ever touching the reel bar.
Crab cage method
Fishing rod method
Cast a rod in the Desolate Pocket with as much Luck as you can muster. High-Luck rods such as the Olympian Godbreaker or the Trident Rod, paired with luck-boosting potions, push the Secret odds in your favor. No bait preference applies, so you do not need a specific lure.
Best conditions for the highest spawn rate
Season and weather move the odds more than anything else. Spring paired with Clear or Rain weather is the peak window. Winter still allows catches, but the spawn rate drops sharply, so it is worth waiting for the right season.
| Preference | Best value |
|---|---|
| Location | Desolate Deep (Desolate Pocket, Brine Pool) |
| Season | Spring (Winter works but is much rarer) |
| Weather | Clear or Rain |
| Time | None |
| Bait | None |
| Sources | Fishing Rod, Crab Cage, roaming spear/harpoon |
How to know you caught it
When the crab hooks on a rod, a Secret Exclamation icon pops above your character and a shimmering sound plays, the standard cue for every Secret fish. Its resilience is only 500, rated Very Easy, so the reel bar barely moves even with low control. On landing it, your character shouts one of its catch lines, such as “Woah! A Grandpa Horseshoe Crab” or “Oh a wise guy!”
Because it is a Secret, it will not appear in your Bestiary until the first successful catch. Once logged, its entry unlocks and confirms the catch counted.
Weight, size, and value
The Grandpa Horseshoe Crab is a low-value sell at 3.158 C$ per kg, but it grants a healthy 80,000 XP. Weight ranges from a 4.5kg floor to a 20kg natural ceiling, with a true average around 7kg.
| Stat | Value |
|---|---|
| Rarity | Secret (luck-favored) |
| Resilience | 500 (Very Easy) |
| Min weight | 4.5kg |
| Average weight | 7kg |
| Base weight | 9.5kg |
| Max natural weight | 20kg |
| Value | 3.158 C$/kg |
| XP | 80,000 |
Size tiers land at Tiny under 2.3kg, Small under 4.5kg, Big above 9.5kg, and Giant above 18.9kg, which helps if you are chasing a specific size record.
Keep in mind the name is shared with a separate Grandpa Horseshoe Crab boat, which is a code-only reward rather than a fishable creature. The fish covered here is the one you pull from the Desolate Deep, and with the right Spring weather and a bit of Luck it will not take many casts to add it to your Bestiary.
