There is insufficient evidence about the century-old statue which is allegedly underwater below the Trincomalee temple.
The image quality is not high enough to verify whether the red kumkum is real or digitally added. We couldn't find any other versions of the same image online with a credible date and time stamp or any attribution to the place and the photographer.
A local scuba-diving service provider 'Taprobane Divers' posted on its blog and Twitter in 2016 a picture of the alleged Shiva or Mahadev statue. The image is from a different angle, and the statue does not appear to be in an upright position.
In 1956, the Arthur C Clarke discoveries from decades ago uncovered underwater masonry, architectural, and idol images of Trincomalee's temple ruin. In his 1957 book, The Reefs of Taprobane, Clarke identified at least 3 Hindu temples built on or around Swami rock over the millennia. There are limited pictorial or video evidence of the underwater ruins online, mostly posted by locals, with none of them featuring the statue in question. There are no local reports or traceable images online to confirm whether locals worship the underwater statue. Customarily, damaged statues or idols of Hindu deities are deemed unsuitable for worship.