A seawall element and installation apparatus therefor, the seawall element
including an elongated plastic tubular member having a uniform hollow
elliptic or oval-shaped cross section and open at each end thereof. The
tubular member has a cylindrically-shaped male portion and cavity
interlocking arrangement for interlocking two side by side tubular
members together by slidable overlapping substantially watertight
engagement lengthwise of one tubular member to another. A seawall
structure includes a plurality of these seawall tubular members
positioned side by side in self-locking engagement to form a row and
supported by being supportively embedded into the earth. An elongated
cast concrete reinforcing cap extends along and interconnects an upper
end portion of each of the seawall tubular members and extends
monolithically into each of the tubular member upon deployment. An
apparatus for water jetting each tubular member into bottom ground is
also disclosed.