Im playing with SE and some other mods, and wenn i made a base in an ocean and startet using artillery they did "burrow" ther way to the ocean island with the artillerie, is that intendet to happen that they burrow underneath water?

Yes. That's exactly how it was intended.
An attempt to destroy a squad with artillery leads to a targeted attack from underground, in a straight line.
Solves two problems:
Removes lags (up to a drop to ~10 UPS for a long time)
Makes you think about protection for artillery

Alright thanks!

Alright thanks!