The Anchored Cross, or Mariner's Cross, is a stylized cross in the shape of an anchor. It is a symbol which is shaped like a plus sign with anchor

Anchor

An anchor is a device, normally made of metal, that is used to connect a vessel to the bed of a body of water to prevent the vessel from drifting due to wind or current. The word derives from Latin ancora, which itself comes from the Greek ἄγκυρα .Anchors can either be temporary or permanent...

-like protrusions at the end of each arm, hence the name Anchored Cross. The symbol can be used to signify 'fresh start' or 'hope'.

Anchored crosses are occasionally a feature of coats of arms

Coat of arms

A coat of arms is a unique heraldic design on a shield or escutcheon or on a surcoat or tabard used to cover and protect armour and to identify the wearer. Thus the term is often stated as "coat-armour", because it was anciently displayed on the front of a coat of cloth...

 in which context they are referred to by the heraldic

Heraldry

Heraldry is the profession, study, or art of creating, granting, and blazoning arms and ruling on questions of rank or protocol, as exercised by an officer of arms. Heraldry comes from Anglo-Norman herald, from the Germanic compound harja-waldaz, "army commander"...

 terms anchry or ancre. The Mariner's Cross is also referred to as St. Clement's Cross

Pope Clement I

Starting in the 3rd and 4th century, tradition has identified him as the Clement that Paul mentioned in Philippians as a fellow laborer in Christ.While in the mid-19th century it was customary to identify him as a freedman of Titus Flavius Clemens, who was consul with his cousin, the Emperor...

in reference to the way he was martyred.