Hydrostatic? Not so fast. A hydrostatic release, which automatically opens the raft’s canister after it submerges, seems like a great idea. But Reme cautions recreational boaters on buying the upgrade. “Commercial vessels have them and they’re designed to work at water pressures found in 4 to 6 feet of water,” he says. If you’re on a small boat, you don’t want to wait for it to sink that far down before the raft inflates.