The Arc Journal
Claimable from Sharkbone at the entrance to the market square on Waiko, this journal details everything you can complete in the Arc. While many rewards are purchased for chimes, completing this unlocks its own rewards, including titles as hinted at in the stream concerning this. All the different sections of the journal and what to do for each can be found below.
Birds
This (http://imgur.com/04j0rCH.png) page of the journal shows all of the birds to spot and where they might be found. We have also been given what this looks like filled in (http://i.imgur.com/cXtOgJn.png).
Mushrooms
This (http://imgur.com/W4LuhXj.png) page of the journal shows all the mushroom types to collect. They can all be found in clusters that spawn on the main and uncharted isles.
Berries
This (http://imgur.com/VTkWHde.png) page of the journal shows all the berry types to collect.
Kami Spirits
This (http://imgur.com/Ra6ELlR.png) page of the journal shows all of the Bakami and Orokami to collect. It seems that the common versions on the left are collected on the main islands, and the rarer versions on the right are found exclusively on uncharted isles.
Castaways
This page of the journal shows all of the new bottles to be found on the main islands. Once found, you can extract a map from each bottle which you can give to your Quartermaster, which in turn takes you to a unique uncharted island.
Please note that some castaway bottles can appear only on specific days, please check the Runescape Wikia to see if a bottle is active or not:
http://runescape.wikia.com/wiki/Castaways
Finding all of the Castaways is required for the Castaway and Salty titles.
Milky Joel
Bottle is found on the far South-East end of Waiko.
(https://vignette1.wikia.nocookie.net/runescape2/images/d/d0/Message_in_a_bottle_%28Milky_Bay%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519220841)
One-Eyed Willy
Bottle is found near the South-East pier on Whale's Maw.[/li][/list]
(https://vignette2.wikia.nocookie.net/runescape2/images/c/ce/Message_in_a_bottle_%28The_Goon_Docks%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519221418)
Manti Claws
Bottle is found by the stairs leading up to where the Moai head was before the Head of the Family miniquest, in North-West Aminishi, but in the Spirit Realm. This bottle is known to have requirements to appear, so don't be surprised if you don't find it the first time you look.
(https://vignette3.wikia.nocookie.net/runescape2/images/0/04/Message_in_a_bottle_%28Christmas_Island%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519221652)
Swabbie Steve
Bottle is found on far South-East Aminishi near Captain Ekahi's initial location.
(https://vignette4.wikia.nocookie.net/runescape2/images/b/b6/Message_in_a_bottle_%28The_Island_Which_May_or_May_Not_Have_Monkeys_on_It%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519222113)
TzHaar-Gaal-Knot
Bottle can be found on the North-West beach of Waiko, North-West of Rosie.
(https://vignette4.wikia.nocookie.net/runescape2/images/4/4e/Message_in_a_bottle_%28Springbreak_Island%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519222330)
The Cannonballs
Found on the southern shore of Cyclosis, south-east of the positive energy wisp.
(https://vignette2.wikia.nocookie.net/runescape2/images/d/d5/Message_in_a_bottle_%28Cannonball_Run%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519222539)
Azalea Oakheart
Found on the northern shore of the first island in The Islands That Once Were Turtles network, by a mushroom cluster.
(https://vignette1.wikia.nocookie.net/runescape2/images/a/a7/Message_in_a_bottle_%28Eisetes_Cretor%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519222813)
Harley
Found on the southern shore of the second island in The Islands That Once Were Turtles network, by the tortle portal to the third island.
(https://vignette1.wikia.nocookie.net/runescape2/images/2/24/Message_in_a_bottle_%28The_Hamlet%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519223100)
Squick
Found on the west side of the third island in The Islands That Once Were Turtles, underneath the south-western rocks, western side.
(https://vignette4.wikia.nocookie.net/runescape2/images/b/ba/Message_in_a_bottle_%28Quis-land%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519223318)
Salmon Ella
Found next to the southern dock exit on Goshima.
(https://vignette4.wikia.nocookie.net/runescape2/images/a/a0/Message_in_a_bottle_%28Agar_Atoll%29_location.png/revision/latest/scale-to-width-down/150?cb=20170519223534)