bulding temples in sea provinces

[Hattori Hanzo]

hallo, I'm a novice both in this forum and in Dominions 3 - I have a question for the very experienced players:

is it possible in Dominions 3 for a normal race to build temples in a sea province ?
and in which way.. ???

in a recent game that I played I see that one of the other players (early age, Helheim) have build a temple in a sea procince adiacent to one of my provinces.
I asked to him how can this be possible, but he refuse to let me know the right way.

I also searched in the game manual and in many places on the web but I have not find any valid solution..

by the way, I discovered how to build Castles (both with the ritual Living Castle and with the help of a Kelp Ancient commander) and Labs (again with the Kelp Ancient commander), but for what concern the Temple I have find nothing.

can someone of you experienced players help me please ???

thank you !!!