Hey, given your situation, if you ran a search of all kinds of paper and you till couldn't come to a conclusion, you probably have to fusion the methods and create your own protocol. I think people who work in plant pathology may be experienced so you can add more topic tags. Additionally, since you are trying to cultivate marine fungi, salinity and the nutrient limitation might be your major concerns. Good luck.

I have isolated various fungi from wheat, barley and eucalypts using tap water agar. Perhaps using sea water agar might prove useful.

"The plant material was cut into 5mm squares and plated 4cm apart on tap water agar plates, at least 20 sqaures per sample were used. These plates were kept in the dark for 4 weeks. The growing hyphal tips were collected using a sterile scalpal as they appeared over the 3 weeks. Most of the fungi emerged after 2-3 weeks These were subcultured onto a complete medium containing ampicillin to negate any bacterial contamination."

we cant identify the fungi because some Ascomycetes will become Mitosporic as well as Non sporulatin.g I hope Single spore isolation method is desirable compared to others

If the fungus won't sporulate, there are alternatives to single sporing and morphological identification. 

Using a dissecting microscope or magnifying lens you can cut out a hyphal tip from the agar and plate that. It should only be a few cells which will be the one species and reproduce clonally. You can also use the ITS region, elongation factor1 and beta tubulin sequences to identify the fungus.