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Water depth measurement – the most efficient way to reduce the construction costs of a small boat marina

We have been building floating pontoons and small boat marinas for the past 20 years. Our experience has shown that one challenge tends to reoccur: the designing of small boat marinas often lacks accurate data about the depths of the water body and adjacent areas.

It is true that the old hydrographic charts and the knowledge of local fishermen about the underwater topography of the area could come in handy. However, these two are not always available and, as a result, the overall costs of the project could bring surprises. Faults and errors in measuring the depth could result in as much as a 6% increase in the overall cost of a project.

For example, if the total cost of a marina is €130,000, an error in measured underwater depth could cost 6% i.e. as much as €7,800.

Why is underwater depth mapping so important?

When a new or existing project is in the planning stage, the information retrieved from depth measuring helps in decision-making and calculations, such as in choosing the layout and anchorage. The choice of anchors again has a significant impact on the budget of the project.

In general, anchorage consists of three parts: a concrete weight, a chain and a chain lock that is used to attach chains to pontoons. If there is no information about water depth or the information is inadequate, it will most probably cause errors in calculations, such as in the length of the chain.

The rule of thumb is that the length of a chain should be equal to five underwater depths. For example, in a marina where the average depth is 3 metres, the chains should be 15 metres long.

If the depth of the marina basin is 8-10 metres instead of the calculated metres, then a 15 metre long chain would be too short for the intended use.

What is the solution?

In order to solve the above problem, we measure the depth by means of a special instrument and map the depth in the entire harbour area before starting with the design.

This simple procedure will considerably reduce any possible errors and contribute to completion of the project within the agreed time schedule and budget.

Underwater depth measuring – how is it actually done?

The process of underwater measuring is simple and consists of three parts:

  1. When you are designing a harbour, contact us (our contact details are provided below). We will determine the need for depth measuring along with any other details, and agree on the time schedule of the project.
  2. At the agreed time, you will be visited by our specialist, who will bring a boat equipped with all the necessary measuring instruments. The harbour area will be mapped by means of a sensor towed by the boat. The mapping will take a few hours.
  3. Our specialist will download the data gathered by the sensor, making sure that all the data are correct. The completed hydrographic chart will be delivered to you in two days.

Our latest project: Vaheri Boat Harbour

We measured the depth of Vaheri Boat Harbour as part of the designing process and prepared a hydrographic chart of the harbour basin on the grounds of the results. Below is an example of the completed hydrographic chart.

We subsequently continued as the main contractor of harbour renovation. We completed the design on the basis of the hydrographic chart, and then delivered and installed the pontoons from beginning to end. This is the new look of the renovated Vaheri Boat Harbour.

What did the client say about the project?

“We chose Top Marine to carry out our project on the basis of a tender. We already had some experience from last year with the installation of Vaheri pontoon, and selecting your enterprise from the tender proved to be a good choice.

Everything was done on time and precisely, with any delays being due to our side. The service was friendly, communication was simple, and phone calls and messages were answered promptly. The team of installers also deserves praise for their service and professional work!

Yes, we would definitely recommend Top Marine! The completed project looks great. The quality is good and the service is excellent!“

Satu Korpela

Jämsä city, gardener


Measuring of depth and accurate determination of depth is extremely important in terms of harbour construction and carrying out a project, adherence to the budget and time schedule.

If you are planning a new boat harbour or upgrading an old one, please contact us and we will come and help you with measuring the depth.

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