I am planning on removing one of the battery connections on my Personal Water Craft (PWC, Sea Doo brand) when I am not using it for an extended period in order to keep the battery from discharging.
Should I remove:
1) the positive or
2) the negative or
3) either (as "opening" the circuit is all that is required)
Thanks

The NEG off first and back on last....

x 2

Functionally, it doesn't matter at all.
But the rule of thumb is to disconnect first and reconnect last whichever post functions as the GROUND on your vehicle. The reason for this is not sorcery or magic - it is to avoid the sparks that occur when your wrench touches something metal on the chassis/hull while tightening or loosening the battery terminals.
On many PWCs there isnt much grounded metal near the battery.

Oh, by the way, since the mid 1950's almost all domestic vehicles have been (and still are) negative ground. Prior to that, lots were positive ground. Some European cars didn't change to negative ground until early 1960's.
But you can pretty much expect to finf negative grounds on anything automotive or marine thats been manufactured in the last 55 years or so.

I keep mine on a trickle charger year round. Batteries last about 4 years.

I keep my boat and non-daily-driven cars on trickle chargers... but the jet ski lifts do not lend themselves to easy electrical charging. Plus so far this is only an irregular event when I travel.

Why not just install a marine on/off switch instead of fiddling with the connection each time?