We have a faucet attached to the line that goes to a 100 gallon water tank. There are, no doubt, much more elegant solutions, but this one was simple. We open the faucet on the dock side, hook the hose up, and run the hose until the translucent tank in one of the pontoons is as full as we think we need it, then shut the hose off, secure in the knowledge that we won't be paying city water prices to sink our boat.a