Does the target need to be in the same region as the Harpooneers?
No. Normally the answer is yes, but the card text 'above or below' means that normal targeting restrictions are ignored, and the Harpooneers can be in any region (surface, underground, underwater, or in the void). As long as there is an adjacent Water site to the Harpooneers and a minion occupying that water site, it will get pulled to the Harpooneers' location.
Does the 'adjacent Water site' need to be in the same region as the Harpooneers?
No. Because the Water site is not targeted, and because the card text uses 'site' instead of ',' the does not need to be in the same as the Harpooneers.
Market
$0.15
Low
$0.08
Median
$0.21