A Tension Leg Platform (TLP) consists of a
structure held in place by vertical tendons
connected to the sea floor by pile-secured
templates. The structure is held in a fixed
position by tensioned tendons, which
provide for use of the TLP in a broad water
depth range up to about 2000m. Limited
vertical motion. The tendons are constructed
as hollow high tensile strength steel pipes
that carry the spare buoyancy of the
structure and ensure limited vertical motion.
A variant is Seastar platforms which are 
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miniature floating tension leg platforms, much like the semi submersible type,
with tensioned tendons.
SPAR: The SPAR consists
of a single tall floating
cylinder hull, supporting a
fixed deck. The cylinder
however does not extend all
the way to the seafloor, but
instead is tethered to the
bottom by a series of cables
and lines. The large cylinder
serves to stabilize the
platform in the water, and
allows for movement to
absorb the force of potential
hurricanes. Spars can be quite large and are used for water depths from 300 and
up to 3000 meters. SPAR is not an acronym, but refers to its likeness with a
ship’s spar. Spars can support dry completion wells, but is more often used with
subsea wells