At last year's Developer Summit, Jesse van den Kieboom demonstrated how realistic water effects can be applied to a JavaScript based web application (see slides, demo and source). The Prototype Lab modified Jesse's code to work with coastal inundation areas hosted in an AGOL feature service. This sample is based on version 4.3 of the ArcGIS API for JavaScript and three.js.
Click here for the live application.
Click here for the source code.