Measuring sea level

I dont know if this is true or not but i have heard that they have some kind devices that they take out there that will measure it for them..or something like that and what they do is take it out in the middle of the ocean in the boat and just drop it out into the sea and as it hits the bottom of the ocean floor it then measures how deep it is or something like that...but hten again like i said thats just what i have heard...

RADARS and SONARS They are one of the most applied technology to study ocean and measure sea depth. In the process of measuring, a sound wave is usually transmitted in the direction of the sea bed. The time taken for the sound pulse to come back to the sensor is measured and applying the formulae of distance and time, the distance between the sensor and the reflecting surface [ seabed ] is calculated. They also make use of advanced LASERS and other equipment related with sounds and light because these are some forms of energy, that are no so easily affected in water media. The science behind this is very complicated and the measurement of depths of some places like Marina Trench, Pacific ocean is very cumbersome, due to the non availability of advanced technology is hindering with the sea depth measurement, but they have calculated thedisnatnce to be approximately around 36,201 feet deep. bourne

Its a technical thing. If you really want to measure sea level, you need to use some special equipments. You also need to measure the sea level at different points and at different times in order to get accurate data.