Fancy a swim?
This battlemap (presented in the usual multi-page print out and stick together format with no grid, hex grid or square grid plus a massive single JPEG for virtual table top use) shows scattered debris of a suken ship for your party to explore. The accompanying text describes it as being deep but the colourscheme just doesn't work for that, it looks far more shallow. Light tails off pretty quickly when you dive - 10 fold with every 75 m of descent if I recall my training correctly - yet the colours look like no more than a metre or so of water over sand in direct sunlight! If this is a deep wreck the scene needs to be darker and more blue.
The wreck itself is lying on the surface of the sea bed, and is remarkably debris-free although there isn't much left. There are also six sea mines scattered around, so care needs to be taken when moving around the area. A devilish GM could be inventive with underwater currents pushing divers or the mines around even if they are (as shown in the cover illustration) tethered by chains to the seabed.
Useful if your plot involves retrieving something from a wreck or finding out why a ship sunk... lay in a supply of shark miniatures or perhaps a few octopi!