I think it would be cool to have changing tides. This would be an interesting way of expanding islands without expanding the map.
Some islands would have gradual beaches where the "height" of the island didn't change much but the width did and other islands would have steep beaches where the height of the island grew and otherwise underwater caves would emerge.
depending on the type pf island, you'd have to be careful how you parked, you wouldn't want to get beached at low tide.
As a whole day is 24 minutes and there could be
4 tides each period meaning the longest you could be beached is 6 minutes.
Some areas of an island may only be reached during high tide and some quests requiring tunnels to be empty of water could only be completed at low tide.
Yeah, I know this would probably be a nightmare for servers to cope with, but hey, still think it would be cool