The graph does not indicate at what depth! So it pretty useless if it is at one meter. I lived in Tonga, Cook Islands, Samoa and Maldives.
The difference in temp in Tonga was 29 deg in summer and 22deg and less in winter at 12 meters. Almost all tropical places will have a drop in temp during the winter month unless you’re right at the equator. There day light hours or temp change very little