Solution for (affordable) waterproof switch?


I see 3 Design/Performance/Cost requirements.
(1) Avoid OR survive accidental excursion to 3 meter deep end of Pool.
(2) Must be tamperproof.
(3) Must be cheap, <$1.50
Suggested Design/Solutions.
(1) Make a sealed air chamber inside the enclosure to provide positive
floatation. Since the Device is normally installed and in a controlled
position, if accidentally dropped in the pool in any other situation,
it would just float, not sink. No need for IP68 to 3 meters.
(2) Epoxy the neodymium magnet to the thread end of the S.S. hex
head bolt. Hold the bolt so the magnet is near the glass envelope
of the reed-switch. Observe and measure the switching action.
Use this information to establish exact dimensions of the next step.
Locate/affix and wire the Reed-switch near a top corner wall of the
sealed waterproof closure. Drill and tap a dead-end 1/4-20 hole 7/8"
deep in the appropriate location where the wall is more than 1" thick.
Thread the bolt into the hole and verify the reed-switch closes.
Take the bolt back out and thoroughly coat the magnet with heavy
marine grease to prevent corrosion. Re- install the S.S. hex head bolt
assembly into the hole and tighten with 7/16" wrench.
(3) $0.82 Reed-switch, $0.47 Neodymium magnet,
$0.14 1/4-20 x 1/2" S.S. Hex Bolt, $0.06 very heavy Marine Grease.
Total $1.49


Thanks @EricSerdahl the sealed air chamber is a good suggestion. I thought of it earlier on but discarded for various reasons, but may pay off to revisit the concept.
Thank you for the detailed suggestion with the bolt and magnet. My current solution, that works pretty well is a reed switch encased in the epoxy, using a neodymium magnet when shipping the product to keep it switched off. However, I don’t have a good housing for the magnet as pictured in your bolt solution.

Unfortunately my various push button/rocker switch experiments failed to deliver a viable option.