Our subsurface buoyancy are ideal for use on most marine applications.

Specialists for over 30 years

Sub-surface buoyancy

Fendercare Marine provides a wide range of sub-surface buoyancy solutions for its customer’s applications. The extensive range of subsea buoys can cater for any marine application. For more information please register your interest or contact one of our team today.

Subsea buoys

We design and manufacture our sub-surface buoyancy solutions to suit the application and depth rating performance requirements of our customers, ensuring maximum product life and integrity at minimum cost. 

Fendercare Marine provides sub-surface buoyancy solutions for a range of applications, including:

  • Pipeline installation buoys
  • Modsyn™ top-up buoys, general subsea installation buoys
  • Transponder collars
  • Modular subsea buoys
  • Distributed buoyancy modules
  • Submersible/ROV/AUV buoyancy systems 
Our range of subsea buoys covers a number of applications such as pipeline installation, transponder collars and submersible buoyancy systems.

Sub-surface buoy types

Please see below details on some of the products in our range of sub-surface buoys.

Sub-surface floatation materials

Sub-surface flotation materials:

The application dependant material parameters to sub-surface buoyancy include the foam material which forms the core of the product and the external coating. 


For shallower depths, we offer either high-density polyethene foam or expanded polymer foam.

The significant benefit both these foams offer over polyurethane foam, which most other manufacturers will provide for these depths, is that the foams are of a closed cell nature. This means that if the outer skin of a shallow water buoy is breached, our customers can be assured that the result will not be a rapid and catastrophic absorption of water followed by failure of the product.

For deepwater applications, we formulate and process our own pure syntactic foam, into which we then introduce moulded macrospheres to reduce the weight and ultimately the cost of the product.

External coatings:

There are 3 main material possibilities for encapsulating the core of Hippo subsurface buoys:

  • Polyurethane elastomer is a highly abrasion-resistant, reinforceable coating which we can either spray-apply or cast around the foam core. For ultimate durability, this form of coating can be Kevlar™ reinforced
  • Rotationally-moulded polyethylene is a cheaper and more uniform method of mass-producing a protective shell for the foam core in applications where the resilience and flexibility of PU elastomer is not required
  • PU paint is mainly used in applications where the core material is resilient in itself but requires some level of protection from UV degradation

Pipeline installation buoys

Pipeline installation buoys

Fendercare Marine’s commitment is to design, manufacture and supply the best possible solution for your pipelaying buoyancy requirements, using durable materials that can be taken onto future projects, and which will require very little maintenance either during or between pipelaying projects.

To reduce tensions on both vessel and pipeline during installation, buoyancy modules are typically fitted. This can happen either on the laying vessel itself or on land if the shore pull system is being used. We deliver proven offshore technology which you can trust.

The main features and benefits of Fendercare Marine’s unique approach to pipeline installation buoys are:

  • Easily and cost effectively customised to suit specific project requirements
  • Extremely durable outer polyurethane elastomer skin
  • Kevlar-type skin reinforcement available as an option
  • Various foam densities available depending upon the depth requirement
  • Some exclusive foams available of closed-cell nature to eliminate risk of loss of buoyancy due to damage to the modulemodules designed to accommodate your preferred attachment and release system
  • Base designed to fit multiple different pipe sizes
  • One-piece or multi-module systems available

Modsyn™ top-up buoys

Modsyn™ top-up buoys

Manufactured from the same syntactic foam formulations as our ranges of larger subsea buoys, Modsyn™ is the perfect solution when small, configurable amounts of buoyancy are required for cable or umbilical support, as ROV trim buoyancy or as a general-purpose installation tool. Modsyn™ does offer a number of operational advantages over alternative products available on the market: easily lashed via the central through-hole multiple units can be configured together via two other lateral through-holes flat-sided for easy storage on land and easy use on deck.

General subsea installation buoys

We are also able to produce general purpose subsea installation buoys to customer requirements, as in this example of a lashed-on design favoured by one of our customers.

Modsyn™ top-up buoy typical specifications

Product ref Depth rating (m) Nett buoyancy (kg) Total weight (kg) Number of modules Diameter (mm) Height (mm)
MODSYN-S1-0250 250 39 24 1 500 410
MODSYN-S1-0500 500 38 25 1 500 410
MODSYN-S1-1000 1000 36 27 1 500 410
MODSYN-S1-2000 2000 29 34 1 500 410
MODSYN-S1-3000 3000 23 40 1 500 410
MODSYN-S2-0250 250 70 52 2 500 820
MODSYN-S2-0500 500 68 54 2 500 820
MODSYN-S2-1000 1000 64 58 2 500 820
MODSYN-S2-2000 2000 50 72 2 500 820
MODSYN-S3-3000 3000 38 84 2 500 820
MODSYN-S3-0250 250 105 78 3 500 1230
MODSYN-S3-0500 500 102 81 3 500 1230
MODSYN-S3-1000 1000 96 87 3 500 1230
MODSYN-S3-2000 2000 75 108 3 500 1230
MODSYN-S3-3000 3000 57 126 3 500 1230

Modular subsea buoys

Modular subsea buoys

Wherever there is a requirement to moor a floating offshore structure safely, it is highly likely that the mooring system will comprise one or more subsea mooring buoys. The principle of modular subsea buoys is that the flotation modules are mounted onto a through-member made of steel. This steelwork, configured and rated in accordance with customer requirements, integrates structurally within the rest of the mooring system, leaving the flotation units unstressed. The nature of these modular buoys is that the number of modules can be adjusted to meet a specific buoyancy requirement and that any damaged module can be replaced in isolation.

Fendercare Marine’s range of modular subsea buoys offers net buoyancy from 500kg to 20t, at depth ratings from 250m, down to 3000m. Bespoke modular subsea buoys can also be manufactured in larger or smaller sizes, meaning the full offering of all possible size combinations of modules, depth ratings and resulting net buoyancies is near unlimited. Below are line drawings of the mini, standard, large and maxi ranges.

Let us know how much buoyancy you require, and to what depth it needs to be rated, and we will provide a quote for the most cost-effective way to meet your requirement.



Bespoke Sub-Surface Floatation

Bespoke sub-surface flotation:

Fendercare Marine’s combination of subsea materials technology and processes allows us to design and supply products for a wide range of other subsurface applications. These can be as simple as a transponder collar, however, the types of projects we get involved in can also be as detailed as the consulting, design and manufacturing we were engaged to perform for the most complex sets of submersible buoyancy ever produced, our sister company JFD’s deep search and rescue (DSAR) submarine rescue vehicle.

Other areas we have applied our expertise, include combined jumper/umbilical flotation and protection and distributed/riser buoyancy. For the vast majority of work of this type, there are no specification tables which we can provide to arrange standard data into a neat format. Our customers confirm their subsea design and operational challenges and work with us to develop a technically robust and cost effective solution – where we act as an extension of their own engineering capabilities.

We provide the application of our materials, our experience and our expertise to assist our customers in finding the best possible outcomes to their subsea requirements. Contact us now with any bespoke subsea buoyancy needs.

Register your interest

If you’re interested in our range of sub-surface buoyancy aids, please enter your details below and one of our friendly sales team will be in touch as soon as possible.