Driving a 600W Piezo transducer for sonar application
I think you need 346V^2/200ohms=600W
Z at 600W is 200 ohms at series resonance? if valid or V is just rounded down, ok.
then at 12V the impedance ratio is \$(346V/12V)^2=831\$ so the driver sees 300/831=0.36 Ohms
For 1% loss or 6W the transistor ESR (RdsOn or rCE) must be 1%  or 3.6 mOhms.
Next what frequency? and waveform? square wave? then you need twice the peak voltage to get peak-peak voltage at 50% duty cycle for 326Vrms if you spec is valid and thus RdsOn.
The transformer DCR primary winding must be similar to RdsOn or less for same losses and you probably need Litz wire for low inductance and use a half bridge driver with +12V on centre tap. as well low ESL wiring from driver is necessary.
I'll add more details as you show more specs.  on my assumptions.  Do you have a datasheet?
Since this is just peak power, what is the duty cycle and thus average power? 400us/333ms x600W = 0.72W.
You need a well balanced transmission line to prevent pulse ringing and thus false echos from long decay times , which limits your short range.

so the Q must be low 0.7 like in a good RF amplifier or matched impedance at 50% efficiency . Power loss is not a problem but high Q resonance at a 50kHz  frequency with &gt;10 harmonics from a high turns ratio transformer is harder to doand conflicts with shutoff fast response times, than a DC-DC convertor with &gt;50 us response time to loop bandwidth.
Thus I would step up DCDC supply to say get an equivalent load of 8 Ohms or a turns ratio of 5 and much higher cheaper RdsOn MOSFETs supply low power for lower current driver to get 600W peak.

then consider a design for class E audio with 50kHz



Thus with a low turns ratio of 5 is a smarter idea to get 1us decay time on the 400 us pulsed 50kHz carrier, lower current driver and easier to manage impedance ratios.

just an idea.