Primitive equations derived originally by Richardson in 1920's have been considered as the model equations describing the motion of atmosphere, ocean and coupled atmosphere and ocean. In this paper, we discuss the free boundary problem of the primitive equations for the ocean in three-dimensional strip with surface tension. Using the so-called $p$-coordinates and a coordinate transformation similar to that in  in order to fix the time-dependent domain, we prove temporally local existence of the unique strong solution to the transformed problem in Sobolev-Slobodetskiĭ spaces.
"Small-time Existence of a Strong Solution of Primitive Equations for the Ocean." Tokyo J. Math. 35 (1) 97 - 138, June 2012. https://doi.org/10.3836/tjm/1342701347