Alfie Liu

Gamepedia says guardians swim in water and doesn't mention lava. (Or is that not a good source?)

Confirmed for 1.14.4

I'd like to add that this is somewhat important in guardian farms. Now it is significantly harder to adjust the lava drop-chute to leave guardians at 1hp. In 1.13.2 they would drop past multiple 2 blocks tall of lava easily. Now they die at random heights inside the lava even in 1 block tall sections.