Sure: when a large amount of gas is released to bubble up, the average density of the gas/water mix can be too low for the maximum displacement of a ship passin

Sure: when a large amount of gas is released to bubble up, the average density of the gas/water mix can be too low for the maximum displacement of a ship passing above to carry it's weight. Ship drops beneath the surface until it hits pure water or a mix close enough, and most ships aren't built to recover from that.