OBS:
There are no tides on Tanoa. This is a missed opportunity, and the Arma engine did support tides long ago...
EXP:
Realistic tides. Small islands in open ocean tend to have relatively small tides (around 1m for Fiji).
In Fiji, tides are a significant factor in navigation due to the extensive reefs. Reefs which break the surface at low tide can be safely traversed at high tide by small and shallow draft boats common to Arma and Fiji.
Reference photo taken at low tide from south coast of Viti Levu. At high tide this boat can be used. Note waves breaking at edge of reef in distance (approx 500m from water level at high tide)
AFAIK, there are no tides in vanilla ArmA3 maps. There's a mod for adding tides to vanilla maps though, if you want to try out what the tides would be like.
there where once, as far as i can remember.
but as the mod works (it does, i've tested it) bi disabled it, for it doesn't work right. for if you set the tight lower, the high-tight doesn't come up as high, as it should.