Hi, I'm not a regular here and I don't know too much about ponds but I
could use some advice.

While out in the garden found a great diving beetle (I assume, it was
a good 2 inches long!), swimming around, brazen as you like, in the
pond. Grabbed the net and tried to snag it but it plunged and I lost
it. Trouble is, the pond's just been treated with a dose of
unidentified chemicals (unidentified because it doesn't state it
anywhere on the container) to reduce weed growth and the water will be
cloudy for the next four, probably five days.

If everything I've heard about this insect is true it can decimate
fish stocks and I certainly want to scrobble it before it breeds, lays
eggs, or anything of that nature. Does anybody have any tips on how
to get it? Do they surface periodically to breathe or anything? (I
waited for ages but I didn't spot it again.) Are they active during
the day or just in the evenings? Do they hide in plants are on the
bottom or anywhere else I might look? Are they as destructive as I've
heard or am I being paranoid?

Any help on this would be much appreciated as I am housesitting this
pond and would prefer it if the owners didn't come back to find all
their fish dead! Cheers.

PS - dragonfly larvae too - worth worrying about?