They spawn all over astraeos, and they usually have jellyfish near them. All you need to do is shoot the jellyfish with a crossbow and harvest. Should take a couple of them but its fine. Since the oceans in Astraeos are very shallow (with the archelon) its very easy to get silica pearls by killing trilobites. I got 200 after i killed a couple herds. So tame this thing ASAP!

DONT let their babies out of water

Breeding tip babies either need to be in a gigaraptor saddle or in the water or their health plummits very fast by 0.1 growth. Sorry for the category as I didn't know where to put this under.

They will eat berries after taming

To find this wonderful creature, it has a chance to spawn near the Cnidaria. So if you find the jellyfish, you just might be lucky enough to find yourself one of these bad boys. Passive tame using superior kibble or Bio Toxin. Obviously the kibble will take less time, but use what you got.

You can raise babies using their algae.

Tame four or more high level Archelons, cryo them for a few days then release them and level them up in food only. Put them in water and harvest the Algae until you have 40+ stacks in a fridge. You should be harvesting almost two stacks per hour (@x1) . Breed them for eggs and incubate the eggs using a gigantoraptor. Hatch the eggs and immediately drop the baby then cryo it and release underwater. Manually feed them the Algae unit the hit juvenile. Then feed them Mejoberries from troughs.

Seen a few in the swallow waters around herbivore island, seems to be a common spawn point for them

Raising Archelon needs to be done in water. Also they're bugged similarly to when snow owls came out. They eatt berries and eat more and faster then a baby giga. If you thought you could walk away, you were wrong.

The first one I saw was on Lava Island on the Center, it was a 140 and I used it to perfectly tame a high level Pyromane because it's so slow and has a high health pool.

Passive tame. They like to spawn around jellyfish, so take a bary or basilo (your best bet). On center they are in the open water near skull island/redwoods. Superior kibble is really easy to make so just use that --AK