FAA Advisory Circular (AC) 150/5300-13A covers "standards and recommendations for airport design.
" It does not include any restrictions on proximity to bodies of water, but it does make the following recommendation in paragraph 319(a):
It is recommended that the entire RSA and RPZ be accessible to rescue and fire-fighting vehicles such that no part of the RSA or RPZ is more than 330 feet (100 m) from either an all-weather road or a paved operational surface.
Where an airport is adjacent to a body of water where access by rescue personnel from airport property is desirable, it is recommended that boat launch ramps with appropriate access roads be provided.
The actual FARs ( 14 CFR 139, Certification and Operations: Land Airports ) also do not state a limit.
The only reference to bodies of water of any kind is in §139.325 (Airport emergency plan) paragraph (e): The plan required by this section shall contain provisions, to the extent practicable, for the rescue of aircraft accident victims from significant bodies of water or marsh lands adjacent to the airport which are crossed by the approach and departure flight paths of air carriers.
A body of water or marsh land is significant if the area exceeds one-quarter square mile and cannot be traversed by conventional land rescue vehicles.
To the extent practicable, the plan shall provide for rescue vehicles with a combined capacity for handling the maximum number of persons that can be carried on board the largest air carrier aircraft that the airport reasonably can be expected to serve.
So, bottom line: there is no limit, but airports are required to take water into due consideration when developing emergency plans, and the FAA looks at each airport and plan on a case-by-case basis during airport certification.
As for the rest of the world, I have no authoritative information; but as others have posted, it certainly seems like the situation is the same, there being numerous examples of airports worldwide built on natural or reclaimed land very close to water.
aviation.stackexchange.com/users/909/TypeIA
There is no such limit indeed.
Princess Juliana International Airport in Sint Maarten is possibly the most iconic example of airport located near a water body, because of the beach over which airliners fly when approaching RWY 09.
As other mentioned, they are numerous other examples of airports that may be even closer to a water body (i.e. without a beach in between).
image source
aviation.stackexchange.com/users/94/abey
Water is not an obstacle.
There are plenty of examples around the world where runways are built on purpose-reclaimed land and the ocean starts just a handful of meters from the end of the runway.
For some random examples, check Nice-Côte d'Azur or Gibraltar or St. Maarten.
aviation.stackexchange.com/users/959/hmakholm left over Monica
Runway 28L and 28R at KSFO , as well as 19L and 19R, have their thresholds right next to the San Francisco Bay.
If you recall, in July 2013, Asiana Airlines Flight 214 landed short due to pilot error.
In November 1968, Japan Airlines Flight 2 completely missed the runway and landed in San Francisco Bay.
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Not going by Barra Airport - Barra Airport is famous for its beauty - boasting beaches, machair and hills - and all in a small island; Barra is a special place to visit - especially memorable if you fly in because of the beach landing strip.
Washed by the tide twice a day, Traigh Mhor beach is reputed to be the only beach runway in the world to handle scheduled airline services .
See Barra Airport website
aviation.stackexchange.com/users/1715/Gwyn Evans
The answer to the question is yes, there are limits.
I'll expand for ICAO regulated airports, but this is also true for FAA ones.
ICAO defines an area surrounding a runway, called runway strip, which purpose is to: a) to reduce the risk of damage to aircraft running off a runway; andb) to protect aircraft flying over it during take-off or landing operations.
A water runway strip would not reduce the risk of damage to aircraft running off a runway.
It would in fact increase it, so a runway strip cannot be made of water.
The size of the runway strip depends on the type of runway, but it ranges 150 m to 0m (zero) in width, and it must extend 30 to 60 m beyond each end of the runway (or the end of the stopways, if there are any).
So, the runway strip contains at least the runway (and its stopways) and extends beyond it on its ends, and sometimes (depending on the type of runway)
it also extends to the sides of the runway, and it defines the limits to how close a runway can be to water.
Going even further, ICAO defines a Runway End Safety Area (RESA) for some types of runways which further increases the minimum distance of water to the runway.
Airports such as Sint Marteen, where the runway is almost 190m from the water, are just examples of how the runway strip and the RESA are applied as safety measures against aircraft running off a runway.
aviation.stackexchange.com/users/1128/molgar
Here is Albert Whitted Airport , a GA facility in St. Petersburg, FL, which has actually juts out into Tampa Bay.
aviation.stackexchange.com/users/1905/Michael B.
Somtimes planes can either  come up short  or  overrun  a runway, ending up in the water.  Is there some limit for how close a runway can be to the water? Does it factor into the runway safety area that is required to be clear of obstacles (i.e., is water an obstacle)? Is there any requirement for displaced thresholds near water?  I am asking primarily about the US, but information about any other jurisdictions is welcome.
Is there a limit of how close a runway can be to the water?
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<faa-regulations><runways><easa-regulations><casa-regulations><dgca-india-regulations>
aviation.stackexchange.com/questions/2822
aviation.stackexchange.com/users/1696/fooot
There seems to be some difference in opinion about whether regulations exist relating to the building of airports near water. There is concensus on the fact that the presence of water has to be taken into consideration when emergency plans, etc. are made. Many airports are built near water, including runways at San Francisco airportor even on reclaimed land. There is disagreement as to whether there are limits. One opinion is that there are limits and the other is that there are no limits, but that airports have to take account of nearby water when drawing up emergency plans. When certifying airtports, the FAA looks at each airport and each plan individually. Barra Airport is cited as an example of an airport where there does not seem to be any limit. Water is not an obstacle. There are lots of examples where the runway ends very close to the water. There are runways in San Francisco that have their thresholds very close to San Francisco Bay. Barra Airport has a beach landing strip.
There is disagreement as to whether there are limits. One opinion is that there are limits and the other is that there are no limits, but airports have to take account of any nearby water when they are drawing up their emergency plans. When certifying airtports, the FAA looks at each airport and each plan individually. Barra Airport is cited as an example of an airport where there does not seem to be any limit. Although there is no limit, airports have to take account of nearby water when drawing up emergency plans. When certifying airtports, the FAA looks at each airport and each plan individually. Water is not an obstacle. There are lots of examples where the runway ends very close to the water. There are runways in San Francisco that have their thresholds very close to San Francisco Bay. Barra Airport has a beach landing strip.