Foam
Bubble
noun
Water bubbles are bubbles that come from the water. This is usually in the form of foam, but could also be a bubble.
水泡 is a literary word, mainly seen in the idiom 水泡に帰す (to come to nothing). This phrase paints a picture of your efforts going down the drain, turning into foam or bubbles in the water, and ultimately disappearing into nothingness.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
データを保存する前にブラウザがクラッシュしてしまったため、長文のメッセージを書いていた努力が水泡に帰してしまった。
My browser crashed before I saved my data so my efforts to write a long message ended in failure.
An update is needed before you can continue but you have more than one WaniKani tab open.
Finish up what ever you are doing on the other tab(s), then close them to continue.
The update will complete automatically once the other tab(s) are closed.