eric wrote:
I would recommend the AN/SLQ-32 detector system. It is kind of old, but
does the job.

There may be more appropriate choices. :-)

http://ssca.org/DiscBoard/viewtopic.php?p=20241 has some useful information.

We have a Tamaya Marine Check. As the above link says, it works well and
is economical on batteries, but you may have trouble finding a source.