CommScope ConQuest Conduit Construction - Manual (Page 34)

4.16 Underground Installation Methods
Submarine Installation
Submarine Construction
Occasionally there will be a need to install conduit underwater, crossing
a tidal basin, lake, or river. While conduit is suitable for this application,
it requires special installation procedures to address the buoyancy of the
conduit.
A logical route must be planned based on what is believed to be down
there awaiting the conduits. Then a route survey must be done to
determine actual terrain conditions, and the route adjusted accordingly
before beginning construction.
Research is required
before a conduit lay
is even planned and
regulatory approvals
must be obtained.