Allow the player to have some control over the bubble movement on the Plane of Water with some increased risk, by biasing the direction of the bubble they are in if they are standing on its edge adjacent to water. The bubble will move in that direction.

Have some water demons, moccasins and nymphs appear on the Plane of Water, in order to imply that this is the dimension from which they’re being summoned into fountains.

Add whales, which can engulf you. Several of them spawn on the Plane of Water.

Replace the Plane of Water bubbles with an initial map looking much the same with bubbles of air surrounded by water. However, instead of the bubbles moving on paths, run a fairly slow cellular automaton that shifts the water around gradually and will eventually join up the air spaces. It’s possible for a bubble to collapse completely, but not if the player’s in it.

Using fire on the water on the Plane of Water boils the water away and opens up air space, but spawns in steam vortices.

Redesign the Plane of Water: instead of moving bubbles, there is just a lot of water and little land; the water constantly sloshes around, changing the land and forcing the hero to follow it, but not every turn like the bubbles.

Moon phases affect the Plane of Water somehow.