You mean just at the end?
Poly pipe wants to float, so I attached a red brick every 10 feet or so -- using copper electrical wire and a cable-tie on each brick. (These particular red bricks have large holes manufactured in them). The pipe was then run between the pilings of a permanent dock.
The entire 10-year-old assembly
is over-engineered: It has dual foot valves attached to a vertical stainless steel pipe "T" and is anchored in a concrete-filled tub in 15' of water. It stays in all year 'round.
My neighbor (to the west) tied
their foot valve to a concrete block using solid-copper electrical wire. They dropped the whole works into the lake and never had to move
any of it since.
For 50 years!