High-voltage jet drive for a boat? Sounds like a "high power" application and I'd go with an off-the-shelf ESC that's already been (hopefully) thoroughly tested and debugged. The concept of an H-bridge is simple enough but once voltages and currents get high, there is lots of potential for destruction if you aren't supremely careful with design and implementation.
Of course, the "con" of an ESC is the higher cost, but without knowing your budget or constraints it's hard to advise.
The Basic Motor Driver
: simple, inexpensive motor driver for 1 stepper motor or 2 DC motors