ERROR - MESH SIZE

Good night,
I am having an error starting a simulation of piezoacoustic model of a sonar with a mesh size of water domain for maximum analysis frequency of 100 kHz :

"Failed to find a solution for the initial parameter.
Out of memory during LU factorization.
Returned solution is not converged."

I am not having this error when I do my study with a larger mesh size (for maximum frequency of 50 kHz)

Could you help me with any sugestion?

Thanks

Diego