You can buy Item Maps for each area which will reveal the location of collectibles.
#1: Spider 01
This is the only relic that won't appear in your map. You can get this anytime while you're in the cave with your friends.
#2: Spider 02
#3: Spider 03
#4: Spider 04
#5: Spider 05
You must find the cave entrance to the southeast, after the broken path.
#6: Spider 06
#7: Spider 07
#8: Spider 08
#9: Spider 09
#10: Spider 10
#11: Spider 11
#12: Spider 12
#13: Spider 13
#14: Spider 14
#15: Spider 15
#16: Spider 16
#17: Spider 17
#18: Spider 18
#19: Spider 19
#20: Spider 20
#21: Spider 21
#22: Spider 22
#23: Spider 23
#24: Spider 24
#25: Spider 25
#26: Spider 26
#27: Spider 27
Clear the Old Mines outpost and check the mines behind it. The relic is found along some loot boxes in a small ruin.
#28: Spider 28
#29: Spider 29
#30: Spider 30
#31: Shark 01
#32: Shark 02
#33: Shark 03
#34: Shark 04
#35: Shark 05
#36: Shark 06
#37: Shark 07
East of Rust Yard outpost
#38: Shark 08
#39: Shark 09
#40: Shark 10
#41: Shark 11
#42: Shark 12
#43: Shark 13
#44: Shark 14
You have to enter the cave northeast of the relic's location then swim underwater to find it.
#45: Shark 15
#46: Shark 16
#47: Shark 17
#48: Shark 18
#49: Shark 19
#50: Shark 20
#51: Shark 21
#52: Shark 22
#53: Shark 23
#54: Shark 24
#55: Shark 25
#56: Shark 26
Found in the same temple as Spider 26, in the submerged room.
#57: Shark 27
#58: Shark 28
You have to jump inside the cavern and dive to find this relic.
#59: Shark 29
#60: Shark 30
#61: Boar 1
#62: Boar 02
#63: Boar 03
East of Amanaki Outpost
#64: Boar 04
#65: Boar 5
The opening to the cave where the relic is is blocked until you complete more missions. I found this open after meeting Citra for the first time.
#66: Boar 06
#67: Boar 07
#68: Boar 08
You have to blow up the stone door using a C4.
#69: Boar 09
#70: Boar 10
#71: Boar 11
#72: Boar 12
#73: Boar 13
#74: Boar 14
You have to blow the wooden signs covering the hole to find the relic inside.
#75: Boar 15
#76: Boar 16
C4 required to blow up the stone door
#77: Boar 17
#78: Boar 18
#79: Boar 19
#80: Boar 20
C4 is needed to blow up the stone door.
#81: Boar 21
In the mine behind Dry Palm Storage Depot
In the same island as Orphan Point outpost
#82: Boar 22
In the same island as Orphan Point outpost
#83: Boar 23
#84: Boar 24
#85: Boar 25
#86: Boar 26
#87: Boar 27
#88: Boar 28
#89: Boar 29
#90: Boar 30
#91: Heron 01
#92: Heron 02
#93: Heron 03
#94: Heron 04
This is accessible via glider. Refer to the video below for more details.
#95: Heron 05
#96: Heron 06
#97: Heron 07
#98: Heron 08
#99: Heron 09
#100: Heron 10
#101: Heron 11
Getting on top of the rock is a bit challenging. Refer to the video below for more details.
#102: Heron 12
#103: Heron 13
#104: Heron 14
#105: Heron 15
#106: Heron 16
#107: Heron 17
#108: Heron 18
#109: Heron 19
#110: Heron 20
#111: Heron 21
#112: Heron 22
#113: Heron 23
#114: Heron 24
To reach this, you have to scale the rocky cliff as shown in the images below.
#115: Heron 25
#116: Heron 26
Just follow the trail until you reach the peak of the marked mountain range. It is inside a cave, on a small altar inside.
#117: Heron 27
#118: Heron 28
There's a mountain trail to the northwest that you can use to reach this relic.
#119: Heron 29
#120: Heron 30