I take the plug out which is towards the top of the pontoon and get all the water out.
I have a 2005 G3 suncatcher 22ft. I have leak on right side ,port, my plugs are on the back of toon 1/2 in up from bottom.
last year i noticed sloshing around water when i puled up to refuel at station, Toon was on trailer where I could hear it. I had this toon 2 years. When I got to ramp and out of way of others I pulled plug. I drained out 60 gallons of water, i had 5 gallon bucket to use for measure. I have searched allover ,under, around the 2 toons, I put a valve( like on tire )
so I could put air in it, ONLY put in about 3 pounds pressure, I found one leak up front where the "splash guard" is welded on. I fixed it, but still will get about 5 gallons on a Saturday -Sunday outing, I called G3, they said do exactly what I did, So I still take on some water.