I was swimming in the ocean in survival mode, then I drowned and respawned and changed to creative mode. I equipped a potion of Night Vision (8 min) and a Trident, then teleported to the ocean and tried to drink the potion but it didn't work. The animation and sound worked but it gave no effect. I exited to the title screen and entered the world again which fixed the problem. I've had the problem a couple of times, even without dying but can only remember having teleported before trying to drink the potion.