I have generally used Raymarine Bidata instruments, but they required thru-hull installation. Almost all of my boats, and there have been many, utilized thru hulls for instruments, raw water, drains, etc and I've never encountered any issues. Proper installation and maintenance go a long way to success and reliability. That said, I have also used a Garmin chartplotter with an epoxied on in-hull depth transducer with excellent results, including accurate speed, and knowing where the dickens I am! I also used a Hawkeye depth sounder with epoxied in transducer and it was junk.