You are looking for a 2ml Magnetic Vial that shouldn't be too hard to see.
Please make sure the lid is fitted back correctly before replacing as the two are separate and the cache will end in the water !
A stand aone cache which we placed while checking our SUP series nearby. It is in plain view and placed by Mrs R as I bottled it !
Please be careful when retrieving and replacing for your sake and the sake of the cache ( mainly the latter 
).