20 Foot Shark at Block Island: Size, Species, and Safety Facts

What size shark is 20 feet at Block Island

A shark reported around 20 feet near Block Island typically indicates a large white shark or, less commonly, a large mako or basking shark. Block Island sits in the Atlantic off Rhode Island, where seasonal waters attract migratory sharks. A 20 foot shark is exceptionally large for most species and commands caution from mariners and beachgoers. This overview explains which sharks reach this size in these waters, how such sizes are measured, and what documented behaviors and risks exist for people in the area.

Which shark species reach 20 feet near Block Island

The white shark is the species most often associated with 20 foot individuals in Atlantic waters around Block Island. Great whites migrate through these waters seasonally, following seals and schooling fish. Mako sharks can exceed 12 feet, with rare reports near 15 feet, while basking sharks filter feed and commonly reach 20 to 30 feet. However, basking sharks are generally not a direct hazard to people. Accurate size reports matter for safety messaging and conservation, as different species have different behaviors and legal protections.

White shark size and records

White sharks mature late and grow slowly. Males commonly reach 11 to 13 feet; females 12 to 14 feet, with larger specimens documented in offshore waters. Individuals over 16 feet have been recorded in the North Atlantic, but confirmed 20 foot white sharks are rare and historically notable. Historical catches and scientific tagging around New England provide the primary evidence for maximum size, though modern protections limit direct measurement. Reported lengths should be treated with caution when based on visual estimates from boats or surfacing events.

Other large species in regional waters

Shortfin mako sharks may approach 15 feet, while blue sharks, oceanic whitetip sharks, and thresher sharks are typically much smaller in these waters. Basking sharks, though plankton feeders and nonaggressive, are frequently seen at or around 20 feet during summer months. These filter feeders pose minimal risk to humans but can be confused with more aggressive species at a distance, underscoring the importance of species identification for boaters and responders.

How size is measured and reported

Shark length can be total length or fork length, and methods affect reported numbers. Total length from snout to tail tip requires precise measurement, while visual estimates from a boat often overstate size. Scientific research uses tagged individuals and caught specimens; recreational catches, when legally landed, are documented by state and federal agencies. Observer programs and photo evidence help verify large size claims. Discrepancies between initial reports and later verified measurements are common, particularly for sharks observed near boats or in surface encounters.

Behavior, movement, and seasonal patterns

White sharks in the Western Atlantic follow seasonal prey, such as gray seals off New England, leading to higher presence in summer and early fall around Block Island. They are energetic, fast-swimming predators capable of surface breaches and swift strikes near boats. Makos are also active hunters, while basking sharks slowly filter feed at the surface. Understanding movement patterns helps boaters anticipate encounters and maintain safe distances under best practices.

Safety practices for boaters and swimmers

For boaters, maintaining distance from surfaced sharks and avoiding chumming near popular swim areas reduces risk. Swimmers should heed local advisories, avoid areas with visible seals or seabird activity, and stay close to shore in organized swim zones. If a large shark is observed nearby, exiting the water calmly and returning to a secure vessel or shore is recommended. Sharing verified sightings with local authorities improves regional data and public safety messaging.

Fishing, conservation, and legal context

White sharks are protected in U.S. Atlantic waters and cannot be harvested; makos face strict regulations and size limits in commercial and recreational fisheries. Basking sharks are also protected under certain jurisdictions. Interactions with protected sharks require adherence to release protocols and reporting procedures. Responsible handling and accurate reporting contribute to science-based management and long-term population health in waters around Block Island.

Documented size examples and summary table

Documented lengths for sharks associated with Block Island waters illustrate the scale of confirmed records. The table below summarizes verified size records by species relevant to the region and highlights the rarity of confirmed 20 foot individuals.