Glass Fibre Reinforced Polymer (GFRP) gratings are normally manufactured by moulding and pultrusion process. It may consist of various combinations of glass fibre and resin. Even though GFRP gratings have been used widely in normal environment, the use of it in offshore is lacking due to the uncertainty associated with the durability and strength performance. In this paper, a total of twelve GFRP gratings, divided into two groups of moulded and pultruded were tested to failure in flexure. It consists of glass fibres bonded with vinyl ester, polyester and phenolic resin. Prior to the flexural tests, half of the specimens were submerged in synthetic seawater at an elevated temperature of 60 °C for the period of 2 months and the other half was left at room temperature. The results show that most of the submerged gratings experienced strength degradation with varying percentage of reduction. The modes of failure were observed in flexure and shear.