Boiling the wood leads to it breaking down faster than if it seasoned naturally into driftwood. Green (fresh) wood will also release sugars and tannins into your tank that will tax your filtration and tint your water. Some woods may contain sap that can irritate or harm your fish. If you coat a piece found in the woods, use 2-part epoxy. Epoxy will provide a water-proof coating that is inert to your fish once it has cured fully. You'll likely have to anchor the piece to slate to counter any buoyancy issues.