The wide angle wet lens I’ve been recommending most often to people since it came on the market is INON’s UWL-95 S and in particular their XD bayonet mount version. This article explains why in my view it’s the best value option on the market.
Get the best from your Olympus TG5 underwater. Part one: Accessories
What makes a good underwater camera ? Part 3 The ability to add a wide angle lens
When shown someone's underwater pictures and asked how to improve them the most common thing the Alphamarine team find themselves saying is 'get closer'. Reducing the distance between you and your subject means less water between the camera and what you are photographing. What a wide angle lens allows you to do is frame the same subject in your picture but from a much shorter distance.