This quest is offered by Argirion (31.1s, 62.7w) who is located near Buckland on the East side of the Brandywine bridge. After recieving the quest head North while searching all the contents (I picked up 75 bottles and 10 kegs just in case) along the river banks until you find Aranhir (14.6s, 61.7w) on the West bank. After talking to Aranhir head back to Argirion to complete the quest, then turn to Mindambeth to barter your items.
There are 2 types of items along the banks of the river a Waterlogged Crate which yield a Bottle of Ale and Keg of Cram which yield a Keg of Cram. Mindambeth (31.1s, 62.7w) is next to Argirion and will barter these items:
Mariner's Hat and Eyepatch requires 25 Bottle of Ale & 10 Keg of Cram
Mariner's Hat requires 25 Bottle of Ale & 10 Keg of Cram
Mariner's Eyepatch requires 25 Bottle of Ale & 10 Keg of Cram
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Hints:
-First thing I suggest is mapping at the milestone in Buckland because it is a long swim.
-Also you can search the items before recieiving the quest.
-Ananhir is located close to his wrecked ship and on the map close to the V in Brandywine River.
-There are plenty of kegs and crates that respawn very quickly so either river bank will be succesful and no need to change sides because of the high cliffs.
-The quest is marked as level 10 but it takes you thru Evendim which is a 30+ zone. Dont worry because you can swim the whole way...slowly...but without danger.
-There are 3 different bartered items but they all go in the head slot. So if you just like the hat, just the eyepatch or combined it is your choice.