If you are standing in Hawaii, you may know you are on an island, but you cannot usually see that you are on an island. A map will show that you are on an island. The shapes that are made on maps by the boundary of the ocean are one type of landform. These include islands, smaller bodies of land surrounded by water; archipelagos, chains of islands; capes, linear extensions of land into the ocean; coves, small pockets of ocean surrounded on at least three sides by land; estuaries, the pockets formed by the mouths of rivers where they pour into the ocean; isthmuses, narrow bands of land joining two larger bodies of land, with ocean on either side; bays, large pockets of ocean that are smaller than gulfs; gulfs, very large pockets of ocean between very large land masses; peninsulas, large extensions of land into the ocean from larger land masses; and straits, narrow necks of ocean passing connecting two larger bodies of ocean.
The junction of ocean and land also creates characteristic land features. Smoothly sloping areas where crushed organic minerals have deposited as sand are called beaches. Steep junctions create ocean bluffs. Long, shallow junctions with very low lands create salt marshes and mangrove swamps.
Below the ocean, there are a number of submarine landforms. The continental shelf is a relatively gently slope reaching from the coast into the ocean. Beyond the shelf, the ocean drops into a continental slope -- a steeper drop into the deep water. Very deep canyons in the ocean are called abysses, and wide abysses are called abyssal plains. Volcanoes create mounts (that emerge as islands) and ridges of side-by-side volcanoes that constitute volcanic arcs (and island chains). Deep cracks in the ocean floor are called trenches; and the elevated cracks along the tectonic plates are called midocean ridges.