I recently bought (from Steve) a White's Sierra Pulse Pro (SPP) PI detector which is effectively a TDI/SL without a delay adjust (locked at 10 microseconds) and without a conductivity switch (locked in the 'All' position). When I took it down to the creek with the Minor John 5in X 9 in folded mono coil I was disappointed when it floated. Apparently most coils are either for dry land use (thus lightweight) or for underwater use (heavy). I've been spoiled by my Fisher Gold Bug Pro 5 inch round